My fiance invited an old classmate only b/c we invited other people from her class and she thought it'd be rude not to invite her. I decided to add "+guest" on the invitation even though my fiance said not to. Her classmate replies that she is coming with a guest, and buys us a $25 gift (our cost for wedding is probably about $80/head). Needless to say, my fiance chewed me out on that one
edit: The classmate makes $80k/year