I'm a 22-year-old straight male dating a 23-year-old woman. This is by far the most sexual relationship I've been in, which is great, except one part is freaking me out: I recently "caught" my girlfriend masturbating with her roommate's panties. (She knew I was coming over and wanted me to catch her.) It turns out she has a habit of sneaking her roommate's worn underwear, masturbating while smelling them (or putting them in her mouth), and then sneaking them back into her roommate's laundry basket. She has also used her roommate's vibrator and dry-humped her pillow to orgasm. I got turned on hearing about all this, and she jerked me off with her roommate's panties. My girlfriend says she gets turned on being "naughty" and most of her fantasies involve being her roommate's sex slave, me fucking the roommate while my GF is tied up, etc. Our sex life now revolves around the roommate—my GF has stolen a few more pairs of panties and even worn them while I fucked her, and her dirty talk is now almost entirely about her roommate. This turns me on, so I don't really want it to stop, but my questions are: (1) Is this bad? (2) Is this normal? We're conditioned to believe women are less kinky and less sexual than men, and I don't want to buy into that. My girlfriend says she isn't "that weird." I don't know what to think.