The legal age is different in each state. In MA it's only 16. In many it's 18. In some it's 16 if you are under 21. They are all different. You have every right to feel hurt by her lie. Some will jump on you and say you should have known, but that is a crock. I've seen 16 year olds that look 30. Most don't ask for id when asking a girl out. If you want to make it work I don't see the age difference being a problem. If the parents are ok with it then there should be no trouble leagally. If they aren't then you may be in for a rough ride. Keep us updated.