http://www.moraloutrage.net/staticpages/index.php?page=Washington

A person is guilty of rape of a child in the third degree when the person has sexual intercourse with another who is at least fourteen years old but less than sixteen years old and not married to the perpetrator and the perpetrator is at least forty-eight months older than the victim.

Oddly enough, I couldn't find out what happens if she's younger than 14... but trust me, I'm sure the consequences won't be pretty. So, count the months between the two of you once she turns 14, and if you're out of luck, you're out of luck.