Well, many people displaying BPD traits have a tendency to jump from one relationship to the next. However, if you've lived apart for nearly a year then in today social climate that's not all that surprising.
Most states follow the no-fault divorce process where infidelity isn't even a factor for divorce. If you're asking whether you should inform the attachment guy that you're in a divorce or give him clues, there is a risk of things getting sticky if you speak out. Maybe others here can speak out about the pros and cons, but my inclination would to be cautious and let them live their lives.
No children together, married only about 5 years. She has employment, likely little basis for her to seek alimony since these days alimony is usually only short term for the disadvantaged spouse to transition into post-marriage life. Is there basis for the divorce still not completed? Many people with BPD traits perceive themselves as victims so her making unrealistic claims is not surprising.