I would ersonally say that gap is too large, but it isn't that bad. Her parents may think so though :/. I've never seen a freshies parents let her date a senior. Esp. since we all know the one thing on a teen boy's mind.
That's only a 3 year difference. Unless she's really immature you should be ok. It probably doesn't hurt if she is really good looking. Older men date younger women all the time. It's just part of life.