hey summerstorm
im sorry about what youve been through. the push/pull behavior is common of but not unique to pwBPD.
"For about four months, she completely idealized me. After we became intimate, she began to devalue her boyfriend and would also make up lies about him or tell me truths that only seemed to favor her, thanks to her tone and word use. I'm sure much of this was because she wanted something from me (sex) and knew she would get it from me by making me think her boyfriend was awful. Of course, at the same time, she was also picking fights with him and cheating on him, so she wasn't exactly happy with him either."
very difficult to get at the truth behind this stuff. like you say, she clearly wasnt exactly happy with him. important to note that she likely wasnt exactly happy with herself, either.
"Less than a week after she told me she was leaving him for me and even went to look at a house with me, she decided to stay with him and gave me no reason why. She tried to reel me in again a few days later, but I turned her down and told her that I'm not going through with this anymore. After that, she began to idealize him to me once again ("I'm so happy" and started to devalue me (criticizing me, telling me I'm too clingy, not replying to my texts, barely talking to me at work). Meanwhile, she was still going home and picking fights with him."
i think to some extent, you are increasingly seeing you were a willing and able participant here. it sounds to me like there were attempts at boundaries, but you made yourself available, whether it was as a romantic partner, or a sounding board. i understand how difficult it can be trying to deal with a push/pull situation.
"When she called me from the hospital, one of the first things she said was, "What have you been talking to him about? You didn't tell him anything, did you?"
i sense a bit of shame, and/or projection.
"Her boyfriend is really nice but is very clueless about pretty much everything. He keeps asking me how she could just shut me out, and I keep telling him it's because of her disorder, and he just keeps asking me the same question. Either he knows nothing about BPD or she never even told him that she was diagnosed with it."
let me get this straight: are you friends with the boyfriend? confidantes? whatever one might call it?
":)o you think she is once again idealizing her boyfriend because she sees him as her savior because he called the ambulance, and how long do you think this will last? Is she basically starting the cycle all over again with him? He recently told me that she is back to being the "girl he first met." This probably means that they are having a lot of sex once again and he is in the honeymoon stage."
her boyfriend is preumably her primary attachment. and again, as such, you should take anything she tells you about the state of their relationship, or for that matter, trust your own impressions, with a grain of salt. it sounds like you are both experiencing push/pull.
"2. How likely do you think it is that she will eventually contact me again, considering I've already told her that I've spent a lot of time researching BPD and recently told her that I'm having a hard time differentiating between her truths and her lies? I refuse to talk to her ever again, but that doesn't mean she won't find a way to contact me.
3. Do you think my knowledge of BPD is a primary reason why she cut all ties with me and is also telling her boyfriend to do the same? "
the short answer to number three is yes. we arent professionals and we cant diagnose; attempting to do so can be fraught with peril. compare it to being "called out" by another person, and then told by that person that theyre spending time researching the condition theyve diagnosed you with. how would you react to that? is there a connection between that and the pendulum swinging wildly back to the boyfriend? there may be.
"4. Is it normal for a pwBPD to bounce back and forth between idealization and devaluing? That seems to be what she was doing when she kept going back and forth between leaving him for me and staying with him. And really, at one point, she was arguing very heavily with both of us at the same time."
personally i prefer the term "common" but the answer is yes. it depends on the circumstances.
it seems to me that triangulation is going on here, on all sides. i recommend you read through these:
https://bpdfamily.com/content/karpman-drama-triangle note: According to Bowen, triangles have at least four possible outcomes. Two of which are good and two of which are bad:
a stable pair can become destabilized by a third person;
a stable pair can also be destabilized by the removal of the third person (an example would be a child leaving home and no longer available for triangulation);
an unstable pair can be stabilized by the addition of a third person (an example would be a conflictual marriage becoming more harmonious after the birth of a child); and
an unstable pair being stabilized by the removal of a third person (an example would be conflict is reduced by the removal of a third person who takes sides).
and this:
https://bpdfamily.com/message_board/index.php?topic=108440.0 a great workshop on triangulation and how we become caught up in it.
in this situation, its going to be advantageous to see your role in it.
hope this helps.