Hmm...13, huh? Isn't that the age where you're supposed to ask your best friend to ask her best friend to ask her if she likes you, and then she tells her best friend who tells your best friend who tells you the answer, and then if it's yes, you ask your best friend to ask her best friend to ask her if she wants to go to a movie with you, or for a burger somewhere, or for ice cream or something like that, and then she tells her best friend to tell your best friend to tell you that the answer is yes, but she needs to ask her parents first, so you tell your best friend to tell her best friend...
Or have 13 year olds gotten more direct than they used to be?
Just ask her if she wants to go to a movie with you or get ice cream, or whatever the thing is folks your age do where you live.