Keep up the tension.
She is obviously still emotionally attached to her ex.
However, he does not seem to satisfy her needs.
This is why you come into the picture.
You're in there now, because she has needs that he cannot satisfy. (Sexual mainly, but it seems he doesn't take charge in the relationship either... I may go into that later)
Either you keep this tension building, eventually it will emerge in sex, and you'll be her lover.
or you let her get the upper hand, and lose her.
So, stay on top of the situation, if she decides you can provide for her, satisfy her sexual needs, and get the emotional going as well. She will probably ditch him completely, and you'll get the girl
you see, a girl's needs can be broken down into a three-part model:
Emotional needs,
someone who is a Provider/Protector (this is the part I'm not confident I remember correctly)
and the Sexual.
If she doesn't get all these satisfied she will be compelled to satisfy these elsewhere. (cheat)
You are there because she needs sexual satisfaction... She also, probably, feels a need for someone to dominate her. Someone who can simply be strong with her.
So, show yourself as the man, someone reliable who is confident in himself and his abilities, and Keep up the Sexual tension.
That way you'll provide her needs much more than the ex, who currently is only covering some of the emotional needs.
She'll probably be ready to connect emotionally with you in not long, as long as you show yourself of as the best alternative... Being an Alpha male.
Don't try to suit yourself to her, she doesn't need a guy to pamper her, she needs a little tension, a little excitement.
I think I have explained something here, but I know if I keep it up it'll turn bad, so... Hope this helps
Cheers!