I think it's a really weird idea. I actually asked my guy to try it once, but we both ended up feeling kinda grossed out after about 5 min. I like to clean myself up a bit after a good bumbNgrind, so I'd feel pretty gross when I woke up. I think both parties would have to be considerably fucked up on something very potent for this to happen-say a good fuck timed exactly when you were both coming down from E and after smoking a j or something. I wouldn't recommend it, but, like FDD says, you should accommodate her. It's not always easy for girls to express their sexual wants and needs, so you should appreciate that she's comfortable enough with you to confidently ask you to try this with her. Just try it-what's the worst that could happen besides you both feeling gross after 5 min, huh??