That's a very good point. Taking into consideration that Zoe kills those she has coitus with, its unlikely that she would ever have to deal with this problem in a relationship with Misty. And I agree that Misty only wanted to keep Kyle with her so that she had leverage for Zoe to keep visiting, as she is lonely and desperate for love. Plus, Nan said to Zoe that she would find love in an unexpected place, and considering as Kyle will probably never be the same as he once was, it's more likely that Zoe and Misty will have a lesbian relationship.
Of course, Zoe may also fall in love with the religious-mom-next-door's son, but he seems to have an interest in Nan, who claims that "guys find her hot and that she gets some all the time" - (don't mind me as I throw up in a corner).