Girl I'm dating suddenly has a boyfriend - what's my play?

[CappyAA]

Didn't even read the OP, just the subject.

Your play is nothing. If she started seeing someone else while "dating" you, it means she likes the other dude better than you. The more you try to get her to like you, the more you'll probably annoy her and make her like you less. The best thing you can do (if you really like her) is to give her a bunch of space. If she calls you, great. If she doesn't, maybe try calling her up in a few weeks to meet up for lunch or coffee or whatever. Either way, the more you try and press it, the worse it will be for you.