This is some of the more recent pages from a MLP fan manga series called "Pink n'Green" if i am not mistaken it is done by 0ryomamikado0/xXAngeLuciferXx, who is also been working on two series for Dusk Shine's Love Life and art for Highschool Dragon.

To help set the scene, Pinkie has just publicly announced Spike to be her boyfriend to her friends, much to everyone else's surprise (including Spike himself), after a failed attempt to get Pinkie to think about this decision more Twilight decided to bring Spike back home for a. . . talk. . .

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Twilight explaining how and why she gave up princesshood was awesome. I really wish the show had played around with the idea of Twilight rejecting princesshood. Would have been an interesting episode.

7115539
Yeah but this is so out of character for Twilight. Spike was willing to join in on the welcome to ponyville party Pinkie through them, so it stands to reason that he had accepted her as a friend then, so Spike had been Pinkie’s friend a little longer than Twilight. Twilight had been with Spike since he hatched, so she knows Spike better than anyone. Spike has done nothing but bend over backwards in order to help her, be it cooking, cleaning or bringing her out of her Twilighting. So the shear fact that she thinks Spike is a type of person that needs this warning, it just doesn’t make any sense. And even if this was a concern, it’d only make sense if it was one of Pinkie’s sisters or parents that were having this talk with him, Twilight has years worth of proof that Spike isn’t like this, whereas Pinkie’s parents and sisters don’t.

you have the link to this manga

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Sorry but no, though you can find it with a quick search on Derpibooru, just look it up by its name of Pink n'Green

7115615
To be fair the artist tends to learn a bit towards some anime tropes when writing, and this story dose seem a bit AU. Plus in one of the pages before this (at the party, after Pinkie announces Spike to be her boyfriend) Spike notices Rarity looking at him and he starts trying to think of how to use this to his advantage.

7115866
Ah ok, then yeah, I'm with Twilight on this. Pinkie is a precious mare (when her mane isn't flat or unless someone seemed to have broken a pinkie promise), I'd hate to see her heartbroken.

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https://derpibooru.org/tags/comic-colon-pink+n%27green

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7115866
I feel the way Twilight is talking to Spike here is the same way a love rival talk. The old I accepted that the girl I love chose you so you better treat her right or else.

https://derpibooru.org/images/1620607?q=comic%3Apink+n%27green
If anybody deserve this speech from Twilight, it's Rarity. She going on a date with Thunderlane even though she have a prior engagement with Spike.

7115933
Wait seriously!? I already hated how she treated Spike in the actual show, but that takes the cake.

I got about halfway through before realizing that I was supposed to read from right to left.

7115933
You i have to agree that Twilight is giving off that vibe to me too.

7115521
Talking is for squares.