This sounds like a classic recycle. Your gut feeling about the FB thing is definitely a

. Why would she not want to be seen with you if she is proclaiming leaving you was a mistake and you are the one for her? I have to agree with the other poster here.
When I was being dumped my ex reached out to me to tell me her mother was in the hospital. She also said to keep it between us because if her sister knew she was speaking to me she wouldn't talk to her.
In that same conversation she told me she loved me... .and she was already with the replacement.
I nipped it in the bud and cut off contact. What followed was two years of slander, false accusations and legal threats (by her)... .
threats from someone whose last words to me were: I love you.
Does that sound like love?
It truly is in their
actions not their words. My ex didn't want me to say anything because I was a "secret". She had been badmouthing me for months, months I thought we were doing well, there was another group of people she was slandering me to. She had to keep up appearances.
BPD's need their supporters and enablers.
It's all about needs and attention. I don't believe your ex wants anything more than that. She wants you to be there without any commitment because then she can flit off to the next unsuspecting suitor and say to you, "Well I didn't lie. I told you I wasn't ready for a relationship" and then say, "See, you are always making a bigger deal of things. This is why we didn't work. I am with someone new now. You need to get over it and stop stalking me".
She will flip it all on you and make this YOUR fault... .we know how that story goes.
I am not saying this will happen verbatim. Everyone is different, but that whole FB platform and not wanting to be seen with you would make me think this is because she is talking to more than one "potential" and those potentials are also on FB. Or she is already dating someone in addition to you. If it were me, and again this is just my opinion, I would remove myself from that situation because it's likely to become dramatic and only set you back in your healing.
It sounds like you were doing pretty good when you were no contact. Out of curiosity, what were you expecting when she came back into your life, wanting to reconnect? What were you missing?
I was recycled several times by my ex. I would take her back because I thought I had yet another opportunity to "fix all the things I was doing wrong" (according to her). It wasn't until long after the final discard I realized things weren't all my fault and she had twisted the words and I believed them at my core (such as my example above). I was trying to fix things that weren't wrong at all, they were me, who I am and that's when I realized it didn't matter what I did, we were not right for each other.
PS. I too can relate to the paranoia. Once someone betrays you it's hard to regain trust. I recycled with my ex close to 13x which is obviously not normal and there are a lot of issues on both sides that contributed to that, however I would say by the last long period we dated (a year) I was checked out mentally. I actually had a lot of resentment towards her as a person and I think I was just sticking around until my weight surgery... .I didn't want to be alone but I really was even in this relationship. My surgery was the final nail in the coffin. I am an attractive person and she was concerned I would leave her for someone else. I got a lot of attention after dropping 100lbs and my confidence got stronger.
I won't lie, I considered it.
For me, I know I struggle with the discard because I lost. Does that make me a narcissist? I don't know. I would never have thought like that in the beginning but she affected my life and even my career in such a life altering way there is a part of me that wants her to suffer for what she did. Cognitively I know that is my own ego and pride at play and I am trying to work those things out so I get to a point of indifference and even wishing her well on her journey (mentally, not through direct contact of course)!