Ohio Statuatory Law?

I have been talking to a girl for some time now, when i met her at the club she said she was 21...I have now heard from some people that she was 17. When I confronted her about this she said she is really 18. I don't know what to believe if she is 17 or 18, does anybody know the legalities of this in Ohio and if it matters whether she is 17 or 18...I am in my twenties. Thanks!