What's up with the inappopriate behavior at my birthday dinner. We're all in our 20's?

Talk to your friend, and tell her that you feel they acted totally inappropriate, and that her bf's question to the waiter was rude and embarrassing to you. Tell her that if they want to get passionate, they should at least wait until they are alone, rather than put everyone else in an awkward situation. You will be able to judge from her response whether you need this kind of friend hanging around or not.