Considering that all of the scenes Kristanna has been in so far have only featured 12 year old boys and Shane, I know who I'm guessing the problem was with.

I'm not really adverse to blame Kate M. for Kristanna's bad experience, but in one of those season promos that was released before the season started they showed some sort of dinner party with all the girls and KL was sitting at the table. This is why I think it might be someone else. But at least Marlee narrows it down to only one person.