Thanks so much for your helpful replies, everyone.

I ended up doing a little research on IOP programs as I was not familiar with what that was. It's difficult for me to admit, but in terms of her treatment, my partner and I have only discussed new options like this maybe once or twice in the almost two years that we have been together. Each time, however, she was the one to bring it up, which does give me hope that a part of her does want further treatment in that area, but she may be fearful of taking the first steps. I think perhaps a nudge from me might be helpful in this case, so I'm going to consider gentle ways to bring it up to her. I would never want to force her into something like this. I too have had my own mental health battles and I was always told that I needed to seek the help or "do the work" myself, you know? Like you have to WANT it for yourself before it can be effective? I don't know.

I did want to add that my partner got her Bipolar diagnosis long before she and I even met, and she has indeed had intensive therapy and is still on medication today. I didn't want to make it seem like she was completely untreated or refusing treatment, but I do think that if I float any new ideas to her she might be hesitant. Whether it be because of how exhausted she is due to her work and additional plans she consistently makes in her free time (something I try to gently suggest that she do less of so she can have more recuperation time to herself) or whether it be because the services where we live (the UK) are simply not available for people like herself, she seems to always have a reason to just leave things as they are. For now, at least. As I mentioned before, I do have hope that a part of her would want to try something new. If I had the money, I would 100% pay for private treatment for her, if she wanted it.

I understand that my partner does not have a free pass to say hurtful things to me. I come across as quite a meek character, but if I feel I have been wronged, I do stand up for myself, no matter who it is. My partner is no exception to this, and she knows this. I tell her whenever she has crossed a line or said something unacceptable. What gives me some relief is that she also acknowledges that it is unacceptable, almost always about 5 seconds after she's said the awful thing. While this of course still does not excuse her saying it in the first place, I think she's learning more about herself whenever it happens. She can be quite stubborn at times, so I do feel at ease when she is willing to take responsibility for her hurtful words. I only hope that it can help her see how to better handle these situations, but I don't know how it works. Can BD cloud your judgement to the point where these things can keep happening? Or will my partner be able to learn from her mistakes and go at it differently next time? I'm sorry if this is a silly question, I just want to understand where we are at and where we could be if I was more knowledgeable on the subject.

As previously mentioned, I do love my partner very much, but there have been one or two instances where I have considered leaving. Not forever, but for a trial separation perhaps. I have never said this to her nor have I made official plans to do so, it has always just been a heart-breaking thought that would cross my mind in the heat of the arguments we have previously had. I guess this is something else to potentially float to her as an option, but of course she probably will be upset with that. I know I would be. I also wouldn't want her to assume that I've left her purely because she has BD. We all have things we struggle with, it's about how we can use our love for one another to battle through it, right?

I'm so sorry that this reply got so long. In short, I just want to try to understand my partner better so we can either:
A: Avoid the petty arguments completely
B: Not let the arguments turn into hurtful personal comments

Do you think either of those options are truly achievable? I sincerely hope so.