Maybe it did cross her mind but didn't Ian say something about it can only happen(the cure) if "IT" is done with a vampire slayer?
And apparently PC has two slayers?
Did that happen between Buffy and Spike? I don't think so. Didn't he have to make a deal with the devil to be human again?
You're right, and not between Buffy and Angel either (which had its own problems). Spike dealt with an African shaman to get his soul back, but he's still dead and a vamp. Buffy has now lost the one reason she claimed she couldn't love him.