Is it ok to hook up with a younger (but legal) girl??

I know an 18 year old girl who is very beautiful, we talk here and there but we've never really delved into sexual topics before...I really have no idea if she'd consider having sex or not. Some people say it's biology to be attracted to younger women but other people say it's not natural or something, idk. I guess I'm a little nervous if it would completely ruin our image to those around us.