Just to get back you. I knew her for about a year, she contacted me later but by then I was with a real partner and I just didn't reply.
The feelings of disquiet started about a month or so in, but even from the beginning just little comments made me think.
The one time that things really came home to me was when she struck up a conversation with two scruffy guys on a bus, invited them for a drink with us, offered them a lift home in my car! and then told me later she would stayed with them and had a "lovely" time if I hadn't been there...and she meant it! To begin with these were the sort of comments I laughed off or thought she was joking or trying to make me jealous. Nope, that was how she was.
It became so blatant at the end I just couldn't figure out why she kept contacting me. How do you figure out someone who you spend all your time with who tells you "you would be devastated if you knew what I really thought about you" and again "if you knew what I got up to you would be in tears". Eventually I actually didn't want to see at all but she kept contacting me. The only couple of times I tentatively asked what she was doing I experienced an almost out of control rage.
The energy drain mentioned in another thread I think has a lot to do with being completely unable to "figure out" these people, it just doesn't make sense to any normal person and so your mind just churns without resolution.
She was though terrified of being alone. I suppose that comes with the lack of any inner life or real emotional experience, it was only through other peoples reactions to her that she felt alive.
The reason I am posting here is that recently I came across somone at work, years later, who appears so similar it is almost uncanny. I had almost totally forgotten and certainly have no desire ever to see or know about how the first is. I can now see the signs so clearly in the second, even though just a colleague. So much more I could say about how I've seen the second behave, but afraid of boring you all. Two affairs with fellow workers within 3 months of being married would be a pretty big red flag!