Eh. Sounds like a sexual fantasy, which is surprising, given that you're both into H. Usually, once dope pervades your life, sex becomes an afterthought - a once in awhile, what the hell, this-feels-kind-of-good-but-I-need-some-dope kind of thing vs the all powerful urge you have towards sex when you don't have a dope habit.
I don't know, part of me wants to answer 'stamp bags are cheap enough, give a shot and report back'. The 'mature' (LOL) part of me thinks it's a bad idea - that tends to be a sensitive area of the female body, and with who knows what kind of potentially irritating or even toxic cutting agents in your dope, it's probably not a good idea even with such a small amount of powder.
If you do it, I'd probably go ahead and cook it up like you'd shoot it, filter and all, first.