"Has anyone experienced behavior like this?"
. Are you kidding me? I have experienced most of what you talked about, with my exBPDgf with whom I'm into 2nd month of no contact, and who moved in with my replacement a week after the breakup. My experience:
- She says "I feel I'm gonna end up with you; I love you more than anything; etc." then "I don't love you; I love my ex more; etc."
- While accepting the breakup I proposed but that she drove, she said "you are the best thing that ever happened to me; people like you, we meet once in a lifetime" and then moved in with my replacement a week later
- One day after I broke up with her and she gladly accepted, she called me and sent me constant texts, mainly mentioning about sweet memories and stuff (immediate reengagement attempts). I did not answer
- She used to see my replacement to "end it" with him, while I was waiting at home. I accepted once, twice, but after that I snapped. How many times do you need to END IT with him? She probably was banging him.
- After she claimed she made him understand and he got it, I woke up one morning with 20 missed calls from him.
- I had proof (that I never showed her) that she was even talking to other guys while we were together, which she denied.
- I had proof also that she saw my replacement many times but she also denied, then capitulated and admitted, saying "she didn't want me to make movies in my head".
- She also called him "friend"
- She sometimes flirted with guys in front of me, and I would go nuts on her, and she doesn't think this is wrong; but when I do look at a girl passing by, she rages!
Yes, sex is indeed amazing. But let me tell you, they use it to manipulate you. Those creatures live through others. They want maximum attention, they need to feel wanted, even if you are showering them with caring and attention, they still want more and more and more.
But dude, trust me, I was going nuts. I still love her, but not the real "her". I love the girl I first met, the image of the person she managed to become for me. They purposely use sex when they are at the mirroring stage in order to hook you before you see through the mask, so they can capture you back if their sadistic plans fail. ALL of her exes begged for her. I am the first who dumped her and is not looking back.
Trust me, I lived for years without sex when I was in a LDR. Once they hook you sexually, you feel like you deserve it. Trust me, once you go NC for a while and stop having sex, your focus will automatically shift to assessing the damage she's done, and take an unbiased look at the whole thing from an outside perspective. I learned about BPD AFTER the breakup, and didn't see her / talk to her since. I am blessed to have very high emotional intelligence and can regulate my feelings quite well as I have been through crap in my life. I am also good at seeing through the masks of people. I don't think I'll ever see her again the way I used to, now that I learned about BPD. I probably won't even desire sex with her.
Focus on you. I have been in relationships before and sex was amazing as well. Sex can be managed to be great. You just have to be open and if your girl truly loves you and you truly love her, you can be in an amazingly fulfilling experience.
I suggest you just go NC. These people play games, that will lead you nowhere. They're in a field and people come and go in their life and once you're out, BE OUT. She will always be damaged, and she is NOT who you think she is.
The biggest problem for me was that I do have some pity for her. I passed through a stage where I considered talking to her about BPD. I know she might be good inside. But she is damaged by her upbringing and her weird parents. But my psychiatrist friend told me that it's not my job to tell her she's sick. She is the only one to want to seek help and be convinced of it. So I let it go. Just let her bite the dust a few more times in her life, and she might realize she is f'ed up and go seek help. You have already done your share of caring. She knows who you are to her. If she ever feels better and comes back to you, then you will see. But that's a long way from now. Good luck. Find someone else is the only way to salvation.