Dear Emily,
I think I kind of understand your situation. I also have some situations right now where I just want to scream at people at work, insult them, bring up all the crap they've put me through over the years, and then let the chips fall where they may. Instead, I'm trying to put up some boundaries, bit by bit. For one coworker who's especially bad (yes, I also consider her a "friend" whom I kind of hate), I decided to just ignore her texts if they come after 8PM and on the weekend too. Maybe not 100% but enough to slowly train her to not expect responses from me. I also just today made a rule that I don't discuss any of my work/projects with her unless there's something she absolutely has to know. I have the luxury of not having to go to the office most days right now and in the foreseeable future. So I decided to go to the office less (which probably doesn't help you) but also that when I'm there, I really schedule my day, so that if my "friend" wants to chat, I can just tell her clearly that I can't because I need the block of time for XYZ.
Do you think you can use the boundaries concept I'm trying to use to make your professional life easier?