"we should do something together when you have time."
Easter '13, a couple of months after my ex left she was trying to organize an Easter with friends and family. She had a boyfriend in the marriage and left with said boyfriend. Very bizarre and confusing behavior. BPD is an attachment disorder. I went and it was the last "family" event that I went to. He wasn't there. I made it clear to her that this is not appropriate when you are in another r/s and your acting as if we're still together with the kids present etc. We're two separate families, perhaps
years from now we can have a BBQ together. She wasn't 100% sure with the new attachment and she wanted me to fall back on.
Fear of abandonment - real or perceived is what drives a loved one away. Your ex could be insecure with her current attachments and she wants someone available (you) if there is no attachment available. She may want to test your availability. If she's treating you coldly there's someone in the picture. It's up to you to put a boundary on yourself. You could tell family: " I need time and space to heal. Inviting ex is not a good idea. I hope you all understand." If it was a one time event - a visit out of Province then there's nothing to worry about.
It sounds like you need to put boundaries in place for ex.