I think food sharing should be discussed before the meal comes. I mean it's perfectly ok to say "I don't want to get the same thing so would you mind if I tasted yours" or something like that but don't just dig into someone's plate.
Its a respect issue...new chick should be a lil uncomfortable to do things like that off the bat,i would have blocked her fork back to her plate or told her she paying the bill...of course i dont mean you rawtid i mean these other uneducated,unmannered broads...