I don't understand what all the debate is about. OF COURSE you should f*ck her.
1. You've not gotten any for a while
2. She has straight up told you she wants you
3. She's experienced and sexually confident - she'll be WILD in bed and you'll learn a lot with her
Trust me, by the time she's naked and sucking your c*ck like a vacuum pump, the fact she's a 5 will have completely left your mind, as will your brain's blood supply.
Too much thinking on this board sometimes. Turn your brain off and enjoy the ride.