Well seeing that you two started dating two weeks after she just got out of a 2 year relationship this is one of two things, if not both. 1. You're a rebound and 2. She's using you to make him jealous. She's checking on him to see what HE'S up to, hoping he does the same.
She still likes him, im not going to add "probably", I have a friend that stalks people and I feel like its due to insecurity etc etc and I hate it. But she probably wants to see what he's doing and who he's talking to (another girl), I dont know how you want to approach her but maybe you can figure out how. Or just ask her if she still has feelings for her ex.