Anything is possible. It would make a strange match and a peculiar dynamic that doesn't make a lot of sense to me, however having said that, it is possible. Add to that fact that Jack Ma stepped down leaving a whole that Marissa could fill does make the question you pose more interesting. That said, I don't think it would happen. The bidding war for Yahoo is coming...and the buyer in the end will be Microsoft.
Whenever they get bored with pumping a Microsoft buyout, Apple buyout and Disney buyout Alibaba is mentioned. Adobe has also been mentioned, Facebook is popular and a few private investors pop up now and again. Just about anyone that can afford Yahoo, and a few that can´t, have been mentioned as potential buyers. All that is always missing is a reason other than -they can afford it-.