Hi Jay,
I don't have any experience with genital warts, but I do think it's important that you tell your girlfriend. Especially for your own sanity! The longer you wait to tell her, the more it will eat at you... and it may affect her trust in you, that you would keep something like that from her for so long. I'm sure she would not leave you for having genital warts, more likely it would be because you've broken her trust. So tell her. The sooner the better.
Hmmmm, just reading about genital warts.... You can still infect her even when you don't have any symptoms, and it won't necessarily show up on a pap test...
Soooooo, make sure you tell her. I'll be waiting to hear back