Why don't you just tell her that if she were single, you would ask her out.
Or is that a bad thing to do when she already has a boyfriend? Hmm .. not sure.
It just strikes me that you two have a connection, yet she is going out with someone else.
Maybe she will finish with him, without knowing that you like her, and you could miss out on a summer together.
Perhaps you could tell her that you would ask her out, if she didn't have a boyfriend, but since she does, you hope that you can continue to be friends. Or something like that.
And perhaps she just likes you as a friend.
Good luck & welcome.
