How about going slow with it, and while your being honest, she will have to know eventually that you JUST got out of a 4 year thing, so she can decide if she wants to be a rebound, or not.
That's not something you talk about on a second date though, but eventually when things have progressed.
Until then have fun, and don't get in to deep, to fast.
Can't young people just date without getting carried away by their emotions? No wonder I have so many posts, about the same freaking thing.
Sorry for the soap box!