Thank you so much for your response. I thought I'd seen another one earlier before work - I SO appreciate hearing from people and shedding some light on this distressing situation!
I can imagine how difficult it must me for you to be mothering a DD going through this, and now have two GC. We don't quite understand how our son - an otherwise bright, successful professional - fell into another relationship with such a dysfunctional uBPD, not that there weren't warning signs early on.
She definitely moved too fast, literally. Shortly after meeting, she and the one daughter who lives with her moved to the same apartment complex he moved to after selling the home he shared with his wife. When my DH and I first met her last Christmas at an outdoor event, she seemed to be stepping in very quickly to the mother role for his son. And she claimed to have a PhD - in some obscure field yet she didn't affix Dr. to her name and she worked as a store manager... .a job she promptly QUIT after she convinced my son to have her move in once he rented a house. Not that she did much to contribute. Her daughter attended a home school program, where they claimed she excelled - yet when my son came across her grades she had mostly C's and D's. Her son was being raised by her parents one state away and she'd hadn't seen them in the year she and my son were dating; her youngest lives across country with that ex-husband and visited over the summer; she actually seemed nice but the gf called her a "brat". It was at that time she told me her OB informed her she was no longer ovulating - I wanted to ask her how she confirmed that as I know she'd have had to have had certain hormone levels tested - only to bring her tampons at her request to the hospital when she had been admitted for GI testing. How could she have her period if she was "no longer ovulating"? That was one time when I told my son of the

and to be very careful - which after she informed him of the "pregnancy" he swears he was.
With her history of lying, I am inclined to think this is one major one and one last ditch effort to get them together. The reason she finally left, after he had previously told her it wasn't working out but she claimed she had no money to go on her own (and he helped her get a job) was she accused him - typically as a BPD - of flirting with waitresses. He thought it ridiculous but didn't stop her as I imagine she thought he would. In any event, he did consult with a divorce lawyer, well-versed in BPD, who actually discouraged the idea of a PI - said it would only inflame her more should she get wind of it and no telling what she would do then. If - and it's a big if - she truly is pregnant, which the attny doesn't think is true - people would be able to see within the next few weeks.
She claims to be religious, although that is dubious, so abortion is doubtful, but she is very contradictory in her convictions and based on past experience she has done a poor job raising her children. I'm not sure how and why she could consider another. Then again, that's a BPD for you. Look at octo-mom, and what your DD has told you!
Should a child be a reality, we've discussed sole custody with my son. Definitely a consideration. No child deserves to be raised by someone like her, not that I hope it comes to that by any means.
Anyway, thanks so much for providing encouragement. Sounds like a hoax is a very distinct possibility.