There is a risk, Susan.
If I were to wake up after a bout of hypothermia, with a young female curled up against me, I'd have a heart attack. Now mind you... that's not a complaint, but just a promise.

Seriously though, I think that once the initial risk has passed and there is adequate core temperature you don't have to continue applying the human-hot-water-bottles Unless you think the person won't maintain adequate core temp.