I do think that part of Glee is that it is almost satyrically stereotypical
I would also reccomend maybe saying something like "Oh, I hope Santana and Brittany get together!" or something of the sort. If she agrees, it shows she's at least open to the idea of gay relationships. You could even follow it up by saying, "It was good to see people like me represented in the media" or something like that.
It's funny, I once read this old advice book for gays...it suggested asking someone what they thought of the latest Will & Grace episode to see if they were also gay :P