Hmm. When my gf played with us, her biggest advantage was: I made her char. Feat selection, class/race., spell selection.. That worked pretty well.
And she used to talk to me afterwards to understand why certain stuff happened to the group this time (e.g. PC kicks the dragons knee. Dragon eats PC. Player: Why?). That improved her understanding.
Another story involved a girl with a hottiness factor that made a volcano look like a fridge. Convention gaming, 12 players at one table with chars prepared by the DM. Everyone was there and waiting to start. Discussion starts whether we shouldn't split up into two groups because of so many PCs.
Then No. 13 came... asks nicely if she can join too. Noone objects... noone talks about two groups anymore. DM takes her next to his screen... where a minute ago he didn't want to have anyone sitting. He has no char prepared for her... nooooo problem, he has one in his head "as good as made exclusively for her". Game starts... story didn't matter, scarcely noone paid attention, 8 PCs tried to court the girl.
First fight starts, group nearly gets killed because every PC able to carry a sword tries to stand between the girl and the monsters. Not that she had any problems dispatching hordes of monsters with her spells... Somehow she threw fireballs in a level 2 game...
Hours later, we rescued someone (a prince). Dashing, gorgeous, intelligent and not in the adventure before the girl joined us and we were hired to rescue some princess.
Well. In my experience, having sex with the DM does not help... but a DM trying to change not having sex with someone may behave pretty silly.