re: if your girlfriend was studying alone with some guy...

It depends. I studied with this one girl a bit because we did well on a group project together, and I trusted her as a smart person. She had a boyfriend, and I had recently broken up with my girlfriend, and I would have been pissed if her boyfriend didn't let us study together. I was not interested at all though, and I think it was really clear both ways.

But I definitely have a habit of studying with attractive girls. It's just way more fun, and they can be way more motivating that your dweeb friends. I had a buddy that always studied with hard 9s. And after a while, he would ask them out, and they always shut him down. It was hilarious.