To be honest I am really unsure if he lied but it seems that, if anything, she wants him back and that alone can create drama. How did she get your number? Well she must how went through his phone but he must have told her about you and that could've pissed her up because again she must want him. So again that can create drama. And only you know what you can handle but if you throw her out of the mix you will always be second because his child comes first. So maybe it would best that you don't date someone with a child let alone kids.
However I must say that me and my fiancé have a child from previous relationships and there is no drama. He met my daughter father and everything is cool because me and my daughter father have no drama. But I must admit that his son mother tried to cause problems but me and her patched things up. I am not going say were the best of friends but we get along but it was a long bumpy road to get to where were at today.
