OK, thanks a lot for that. Happy Thanksgiving.
If your partner's sexual history is accurate, i.e. no sex with anybody before you, then logically you are the source of her infection. However, genital apposition (i.e., sex without penetration, sometimes called "outercourse") can transmit HPV; if she was a technical virgin but still had some heavy petting, should could have been infected before you. You might never know for sure. And even if you weren't the source, you can assume you were infected; if you didn't have it first, most likely you were infected from your partner.
That the HPV was a high risk type is to be expected; in general, the high risk types are the most common. There is no test to prove whether or not you actually are infected, or to tell if your presumed infection has gone away.
There are no firm guidelines about informing other partners in the future. Most HPV infections clear up on their own after several months. My personal opinion is that once a year or so has passed, there is no need to inform partners. Since most people are going to get sexually acquired HPV someday (including high risk types), regardless of what precautions they take, telling or not telling probably doesn't make much difference in the long run. However, others disagree with me on this and think that everybody who knows they have ever had genital HPV are ethically obligated to inform all future partners. (Many who disagree are people who have had HPV problems themselves and are pissed that a past partner didn't warn them. Most STD/HPV experts agree with my approach.)
Congratulations for apparently having a level-headed perspective on this. It sounds like you're not as upset as some people on this forum have been, and are trying to do the right thing for your current and future partner(s). Good show.
I hope this helps. Happy TG-- HHH, MD