Sorry it took so long to get around to reading this chapter but real world stuff got in the way so I couldn’t read it right away. It was pretty good for a first chapter and it’s always nice to read a Fallout Equestria stories that start out in a stable for a chapter or two. Although, I don’t think the main character is supposed to level up until after they leave the stable. There were some minor grammar errors here and there but nothing an editor or a reread couldn’t fix. Here are some of the ones that were worth mentioning to you in my opinion.

I can’t wait to read the next chapter and I hope to read it soon. Oh, if you like, I could help out as one of your editors if you would like some help. If you don’t want any help and want to do it by yourself then that’s cool too. Just thought I’d ask is all.

Pain shot from my wrist and from the hoof out, it radiated up my leg.

This line could be worded better. It’s written so it sounds like the pain starts at her wrist and then goes down to her hoof only for it to go back up her leg. From personal experience on hitting limbs on something hard, That’s not how pain travels.

Sometimes I couldn't tell if the walls of [or the] lights had the green tint.

The word “of” should be “or the” right there.

Her lavender coat was nicely accented by the bleach-blond mane and tail
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I wanted to watch her colorful orange and yellow mane stand on end and her dark purple coat go pale.

There is a small inconsistency right here. Originally, you said that she had a “bleach-blond” mane and tail but then you said her mane and tail were “orange and yellow”. Bleach blond isn’t the same shade as ordinary yellow so either the second mane/tail description needs to be changed or the first one dose.
Personally, I like the second one with the orange and yellow. Although, if you go with that one you’d need to describe what that looks like (If it’s yellow with an orange stripe or something like that).

You still got yer shower [to ta to] in a bit.

Wait, what?
I think you forgot to finish this part. What is “to ta to” suppose to mean?

and, since she was my secret charge as part of Stable Security, it made guarding her that much easier.

Wait, didn’t you introduce Back Ice as a Maintenance pony? How is she now working for Stable Security?
Normally a character only gets one job in a Stable/Vault unless certain circumstances are explained beforehand. This normally takes place when the character’s setup is being established at the beginning. A small example would be when you wrote that she was working in maintenance killing bugs. Throwing in that she also works for Stable Security near the end of the chapter is a bit jarring and seems to come out of nowhere. Maybe if you had her thinking about how she has to secretly watch over her best friend around or near the time she’s doing her maintenance job or maybe even when she’s eating breakfast, then it wouldn’t seem so random. I guess what I’m trying to say is that it should be clearly written in a way (at or near the beginning) that shows that she has two jobs and why, so your readers don’t get confused about what she does in the stable.

Wait, I just got done reading the first chapter I had pulled up from awhile ago. Where did it go? I'm so confused.