In all seriousness: the age difference might not be a long-term issue as long as you stay flexible about who she is. She's super young and she'll be finding herself and changing a whole lot.
When I started my relationship, my girlfriend was 17 and she's now 26 and the way she thinks and operates is 80% unrecognizable from the girl I started dating back in the day (from a promiscuous, economics/politics-lover, make-up-addict girl to a slow-living, yoga/meditation/vegan/nature borderline hippie cook now. You've gotta stay open-minded
The sex gets way better as she grows out of her 20s, btw, as she understands herself way more over time.