The exact dates don't matter, but the history speaks for itself. You said she suffered from post-natal depression. That could have pushed alot of what was underneath to the surface.
Right now she's going out with these men because she wants validation. She wants to be told (by someone else) how good she looks, how confident she is, etc. because right now she doesn't believe it when it comes from you.
"Interestingly she had been asked out because it was said that she really needed a night out, so maybe shes not enjoying being on her own as much as she thought!"
You're mindreading. First thing you need to do is to stop that. Concentrate on yourself. When she said that she wanted to go out on Friday, you should have mentioned you already had plans.
M-43 W-40 2D - 9 and 5
Emotion, yet peace. Ignorance, yet knowledge. Passion, yet serenity. Chaos, yet harmony. Death, yet a new life.