What would her friend think?

......Well fuck, Equestria just tickled the sleeping dragon and it awoke with Military Grade Automatic weapons. I don't know if I should feel sorry for Equestria or not......Nah!

9530394
Okay, keep informed me when you do the fifth chapter.

I'm only hope that Spike will reunited with Twilight.

So basically...Celestia has no clue (presumably) what her own captain is doing. Way to drop the ball

9581186
'dropping the ball' kinda understates it at this point, celestia put the ball into a cannon and fired it straight down at this point.

I think giving exact model and optics wasn't a good choice, I am curious to see this story continue

Celestia you stupid idiot why do you let your new captain going around killing innocent people that are outside of equestria i hope you open your eyes to see the destruction of your pony's has caused

9609990
She doesn't know about this yet. And even if she did, she would be too focused on Twilight's "death" to even do something about it.

9582169
Also, I wanted to be accurate when portraying firearms usage and the destruction it could bring.

9618592
Wow sounds like she gonna have more enemies as usual

any idea when we can expect an update and new chapter?

9580534
Just be glad they didn't tickle 2019 King Ghidorah.

any idea when we can expect an update and new chapter?

I really like the idea of exiled Twilight stories, but I just can't seem to find one that's actually good. This story is probably the best example I've found so far, but it still has plenty wrong with it.

The single biggest problem is how you keep telling and not showing. Character dynamics are told to us rather than demonstrated.

Flash made it his mission to make the most out of his new life in Klugetown, becoming his boss's personal bodyguard and something of a replacement trainer/big brother figure towards her apprentice. Smolder herself became something of a little sister towards Twilight, who she said reminded her so much of Spike, who in turn was her own former dragon apprentice.

If you want Flash to be a big brother figure for Smolder, try having a scene where Flash acts like a big brother instead. For example, lets say Twilight is training Smolder and Smolder makes a mistake. Smolder is feeling pretty bad about it, and Flash is there to give her an ice cream and some comforting words. The same goes for Twilight viewing her as a little sister. Hell you could use the same day of training for that too. Just have the mistake that Smolder made be something that Spike would have done, and have Twilight reminisce over Spike and think about how Smolder has taken his place. Maybe Smolder was distracted by some gems. Maybe it wasn't even a day of training, what if Smolder started to get greedy and grow like spike did in that one episode. Flash could still be there to cheer her up and Twilight could still think about her and Spike.

Something similar is happening with the couples. I know that you tagged this story a romance, but so far this story is not a romance. The two side couples are introduced and established over a paragraph or two each. The leading couple meet, and literally the next scene that they share are a couple. Twilight and Flash meet at a strip club and twilight names Flash the new captain of her army, for no good reason and despite only having known him for a few minutes at best. Flash, for no good reason and despite only having known twilight for a few minutes at best, accepts her offer. The next paragraph that they share, Flash is referred to as her boyfriend. Speaking of which,

"Wait! I never got your name!"

. . .

"It's Midnight!"

As she turned tail to leave the awed Flash behind, Twilight scowled under her breath at what she saw was a failure to come clean in regards of her true identity. Damn it, I'm already dirty enough as it is... Why should it matter, anyway? Oh, well. I'll tell him my true name once we hit off.

That has no reason to be there. If you had actually had Twi and Flash grow into a relationship then that might have been a nice moment for Twi to tell him her real name. But you skipped straight into the relationship so it doesn't matter.
Smolder and Sandbar are little better.

They were wise enough not to rush into romance with each other, however, and saw to it that their relationship was better developed. Of course, only a year had passed that Sandbar and Smolder decided to become a battle couple and defend their new home from the forces of evil that dare invade it.

You wrote that they decided to take things slow and let their relationship grow, which is good. This at least implies that a relationship is buidling offscreen. However, "they decided to become a battle couple" is dumb. I understand wanting to incorperate a cool trope into the story, but you need to actually incorperate it. It's the same problem from earlier, you keep telling instead of showing. Have Smolder and Sandbar go on a couple small dates to show their relationship growing. Then on one of them, have a surprise attack happen. Maybe there's a random raid by MCO, and Sandbar is forced to fight back against former friends to protect the girl that he loves. You could even have that cool 'two people fighting back to back' thing. Instead of saying "they decided to become a battle couple" have them act like a battle couple. Just don't call them a battle couple in the story. You should never have to explicitly say the trope that you're referencing for the reader to understand it.
Dash and Quibble are probably the best couple here. Mostly because they're the only ones that act like a couple. However they still have the same problem as Twi/Flash and Smolder/Sandbar, in that their actual romance is described in a single paragraph. At least Dash and Pants have a scene where he comforts her, and she's grateful that she has someone who cares.
A romance story isn't a romance because it has a couple in it. A romance is a romance because it's about that couple growing closer and being romantic. You wouldn't call MLP a romance show just because Shining and Cadence get married.

My last big criticism is the battle in chapter 4. I'm gonna put it bluntly, this scene was the worst scene in the story by far. 9582169 pointed out that using real world guns was a mistake and they were totally right. MLP's world has always been very ambiguous on its exact level of technology, so I could believe it if they had lower level firearms like muskets or flintlock pistols. but if upload.wikimedia.org/wikipedia/commons/3/31/M4_Carbine_with_M203_Grenade_Launcher_%287414626424%29.jpg is a regular weapon that twilight can just get and use, then the battles just fall apart. Why is anyone using a sword when they could be using a gun? Even in close quarters, a gun will still win against a sword. Why are the MCO deploying 20000 in a single battle against a force armed with guns? There's a reason that militaries don't fight like this anymore. Once guns became automatic it became just to dangerous to fight like they do here. Not to mention how automatic firearms render most other small arms moot. Why are ponies shooting at Celeano and Flash with arrows when guns exist? How do you expect Celeano to fight with that sword of hers? is she going to charge/fly at someone to attack them with it? This is of course on top of the fact that when reading the line it sounds like laughable wish fulfillment.
The characterization in this scene is baffling as well.

"First ever battle. You nervous, Flash?"

"Yeah. Aren't you?"

"Nope. Why are you?"

"You said so yourself: first ever battle."

Alright cool. Twilight has already been established as a cold blooded killer in the first chapter, so her talking to Flash like this works. What doesn't work is her talking to FLASH like this. Flash was the co-leader of a year long resistance against the changelings remember? and a royal guard to boot. Flash should by all rights have more combat experience than Twilight. Add profesional training on top of that and he should be a better fighter as well.
The end of the chapter doesn't work either. Twilight comes off as slightly unhinged in this story, not really caring about killing and maybe even enjoying it. During the battle you wrote

The aforementioned ground team joined their leaders into battle, specifically targeting those magic ponies in armor. Flash harbored no such desire to kill another living pony, let alone seriously maim him or her; he settled on incapacitation and knock-out maneuvers, instead. Twilight, on the other hand, gleefully made an exception to the rule as she sliced-and-diced any and all pony who was dangerously close to Klugetown.

You literally described twilight as gleefully kiling ponies, so why is she acting so remorseful after the battle?

This whole story is currently in flashback mode, so I get that you're trying to establish important things before going to the present, but you need to go a lot more in depth. Otherwise you're better off just skipping to the present and establishing important details as they come up.

I realise that this whole thing probably reads as being a lot meaner than I meant it to be, but I want you to know what you're doing wrong so that you can fix it. Basically all the other 'exiled twilight' stories have the same general mistakes, but I commented on yours because your story has the most potential. I meant it when I said that this was probably the best example I've found of this type of story, fourth chapter notwithstanding. I hope this doesn't discourage you, and I can't wait to see where you take things after this.

any idea when we can expect an update and new chapter?

9821928
I understand. Keep in mind, these are merely flashbacks. I wanted to balance out the idealism and the cynicism of the whole situation; in short, where there is darkness, there is light. Plus, the relationships and character dynamics were meant to be properly developed, but I had trouble expanding the chapter length out of fear it would become soap opera filler.

But I can see where you're going with this. Thank you for the advice, and I hope not to make these mistakes in the future.

9821928
Also, the usage of modern weapons was meant to give off a modern, almost retro-like, aesthetic. It gives the impression that they're pragmatists in battle, rather than fully relying magic and sorcery. Plus, it may echo the Themyscira battle from Wonder Woman (2017)…except neither of them are the heroes or villains...

There's a lot wrong with this story, but more articulate people have already said what needs to be said.

That said; I'm still going to follow this, because it's an interesting take on a sorta overdone concept.

P.S. I have read "The Forgotten and Exiled". This is already better.