Teabag + polaroid.
Seriously, it would depend on exactly what you mean. If my girlfriend left a note saying that I could do whatever I wanted, I would probably interpret that as her feeling guilty for passing out before the night was over, and I'd do nothing. If it was a specific request for me to do something sexual, as though she had set up this encounter as a fetish, I would do nothing, but would talk about it with her later to find out why she felt the need to incapacitate herself and then ask me to fuck her relatively useless, limp, non-self-lubricating body. Sloppy drunken sex =
. Before I could get into this particular situation, I'd have to understand her motivations behind it. In my experience, this sort of behavior would be a warning sign for unresolved issues involving childhood molestation or rape.