What Do I Tell My "Lovestruck" BFF?

I would say it just as you've said it. It's your duty as a bestie to let her know she's being an ***! If you're willing to spend your time with her than she should be able to put the dang phone down! I would just say something like "Listen you're with me right now put down the damn phone it can wait a few hours." Technology is always there when you leave! As for the boy I would tell her that she's being selfish and to let him know what's up. Just spill that big ol' jar o' beans!