My own flags went up upon reading not that she'd mentioned a guy friend, but is going places with them, I presume alone?

That's the territory that gets to me, personally. Doesn't make me psycho, makes me guarded about the affair potential, emotional or physical. Affair meaning, long term , a bit too close for comfort territory. I've been burned pretty severely in my own past. The first time was because of peer pressure from my boyfriend, awww cmon they're just friends to ohhhh so and so thinks that if we work on this, things can be better because I'm spread too thin and have little energy for you so I'll blame you for wanting what little is left. His marriage after me did result in divorce due to cheating. He pushed boundaries with me, then crossed them with her.
In my marriage, the closeness to a colleague seemed to fill his mind right up, his friend was a cheater on her spouse and it fueled fear onto me. He's bpd, and that's the imaging of threat....1 of 9 criteria.

I agree with rcat's list...