Don't do it. You're being a horrible person to both her and her boyfriend if you go through with it. If you've just gotten over someone chances are you can walk away from this situation with hardly any heartbreak, unless you're really clingy.
So you're going to end up buying dinner for a girl who will then go home to her boyfriend.
Playa
No lol
I mean if she doesn't like me, and just thinks we're good as friends then she will try to split the bill with me, desperately. Just to show that we're just friends...