i agree with everyone so far, the fact that she agreed to this means she's already DTF, so relax and just do whatever normally gets you laid, and don't smoke too much weed and freak out, you probably shouldn't let her do that either lol
prep everything you'll need (snacks, weed, drinks, rolling papers, condoms, lube, snacks, etc.) and double check it, then triple check it to make sure. do whatever you gotta do to get the place ready and make sure nothing will go wrong or c0ckblock you
then just relax however you relax and use your smoothest moves. so long as you don't completely botch anything you're getting laid (you don't have to use super good expert level game here, just don't fvck anything major up and you're good to go.)
good luck brotha