Killing someone, hardly outside the realm of fantasy, unless she were completely sane and willing and I'd be completely assured not to face any legal/social repercussions (or simply no one finds out, ever).

Fucking a dead body, probably (especially if she's still fresh), if I could be sure to get away with it. This is purely a practical concern, I'd rather not get charged with a murder I didn't commit (or even just with whatever the charges are for necrophilia); I hold that, regardless of what happens to your soul/mind/whatever (in whatever shape that exists) after you die, the body is just dead meat and can be used however (which is also why I'm organ donor, as everyone here should be).