[Appocomaster]

Girls do get needy sometimes.
I appear to have discovered this quite a lot recently.
You could just let her go, which would probably be a big mistake unless you a) don't want the hassle or b) really don't like her, which from your comments doesn't seem to be the case.

Do something (good) that she's not expecting. Take her to see something nice, etc. Get back that uniqueness value, and show that now you're better you're happy spending time with her and more importantly on her (in the non-sexual sense; not always the same thing).

If you want her 'back' and to distract her from her ex, either you have to just become the perfect boyfriend ("positive" method), or sort of force her back with you by somehow pushing her away from him and back to you ("negative" method).

Good luck though!