Ladies and gentlemen, I present to you an entire run of a webcomic already made about this character you speak of:
http://www.kiwisbybeat.com/minus.html
More on topic, somewhere out there is a story whose title I cannot at this moment recall, about a very beautiful woman who keeps trying to have a boyfriend and failing because her ambient femininity is so high it gradually turns her boyfriends into women as well.
Generally, I think the idea of touch-mediated transformation is very sexy, but you're going to have trouble finding situations where the author didn't find it easier to just insert an intermediate cause- a girl rubbing breast-enlarging lotion on a friend, a witch casting a magic spell that requires contact as part of the ritual, and so forth.
As the original King Midas himself learned, a power directly controlled by touch is a dangerous thing, no matter how fantastic the initial results.