Looking for find some understanding.

I will try to make this short.

I'm relatively recently broken up with a partner over 6 years because they were unfaithful (multiple times).

She had exhibited flirtatious behavior since the beginning of our relationship, but I wrote it off as it just being part of her personality (which I guess wasn't untrue...)

Things that started to become common for her:

- chatting with guys inappropriately on social media/text etc.
- flirting with them in front of me.
- being overtly sexual to literally anyone she came in contact with.
- going from incredibly happy to incredibly sad randomly
- Never feeling "happy" but unsure of why.
- Tried to break up with me several times, but stayed because of the life being with me afforded her.
- Always getting guys to pay for her drinks/meals.. even if she was with me. She rarely paid for much herself, ever.
- Being a chameleon and only being interested in what the guy she's dating at the time is interested in, has no idea what SHE is interested in.

The first time she physically cheated, was 3 years ago. I thought it was my fault, and forgave her and tried to work through it. We moved into a new house together, and I thought we were going to recover. She started working a new job, and things just seemed to never be the same.. no romance, barely an intimacy, and when there would be, it was just her "doing her duty."

I was always nice to her, cared for her, but I just felt like I was always being taken advantage of for what skills/usefulness I had as a photographer and filmmaker (she's an actress.)

We had a lot of great times, more so than the bad.. but the ONE thing that has driven a wedge between us from the start was her inability to stop seeking attention from other males.

Most of them she wasn't even attracted to, or they'd have a major deal breaker which made me wonder why she was ever into them at all? I found out later, it was just the attention. She likes the attention she gets. Every time she goes out to "hang out with friends" it's not just that.. she's "making an appearance." She has to be the center of everyone's attention at all times.

I finally started to do some research near the end, and started to suspect that she may either be Borderline or HPD or a little of both or a combination of a lot of things. We had a discussion and mutually agreed that our relationship wasn't doing very well, and she wasn't into me anymore. She even suggested I go "find it somewhere else." Suggesting I could go have sex outside of our relationship and she'd be okay with it. She even mentioned "trying an open relationship" which just seemed more like an excuse to validify the cheating she was already doing that I wasn't aware of yet.

But once, we decided to split.. and it actually became real, as in.. I started moving out, seeing other people.. it started to hit her and she became incredibly upset, and even suicidal to a point. I wanted to stay friends with her, because I still consider her to be my best friend and if our lives crossed again after she finds some help I was open to trying again in the future, because I did care about her.

We also work together, which complicates things and since she's made threats of harming herself, I've tried to remain close while still trying to give her space to heal.

There's a small part of me that feels bad, because I think that maybe the cheating she did wasn't something she had control of, but cheating is still cheating...

I'm second guessing my decision to leave, because I see her and she's so sad, like her entire life has been ripped out from under her. I told her that all of her decisions up to this point lead her here, but that she still has the power to change it, but she has to do it herself and for herself, not for me or anyone else.

Since we've split, the first thing she did was went to a guy friends house and slept with him because she didn't "want to be home alone." She begged me to come here several times, and I refused. One night I did because she was threatening suicide, and I didn't want to feel responsible if she did try anything or worse yet, succeeded.

She's a good person underneath her mental issues, and that makes me so sad that I can't be with her because of that.

I guess my question is, did I make the right choice? Could we have worked this out? Could we have mended our relationship after she'd cheated on me (with people I know and have to see every day) 6+ times over the past year? Am I right in feeling sorry for her, knowing that it might have been out of her control due to her mental illness? Am I punishing her for something she had no idea she was doing?

When you think of what you want in a partner do you want the sort of relationship you had with her? If the answer is yes then it was a mistake. If the answer is no then you did the right thing.

You should establish whatever you want from the relationship with whomever you relate to and allow them as adults to decide if they want to be with you under the terms you want or not. By the same token they will have whatever boundaries and terms they set up and you decide (like they do for you) if you think the relationship is worthwhile or not.

When you agree to terms that you are not satisfied with you are being very unfair to the other person. You will eventually become resentful and also may decide to leave the relationship later all while you had been accepting terms you were not happy with.

So when it comes to relationships be selfish and do what you want for yourself. If a person doesn't like the sort of selfishness you express it is very obvious to them and they can make their decision to stay or not stay.

The best relationships are when both people are extremely selfish, getting exactly what they want from the other person and have few if any aspects of the relationship they dislike. Its hard to find one of those relationships if you spend your time in unsatisfactory ones by settling for things you don't like.