Yes, all of the girls chatter about her after that scene was that she didn't wash her hands. And when Meredith was bothered by Derek not sleeping in her bed becuse of her snoring, she said it was for all sorts of things before she admitted it was abandonment issues. And when Meredith and Derek were arguing about whether or not the dog should be put to sleep, it was about their relationship, but they never said that flat out. There is all sorts of talk on the show which is focused on one thing, but about another.
It was an absolutely uncomfortable situation for Callie to be in - walking in to what she thought would be an empty room only to find two people in there. But it was an equally uncomfortable situation for Meredith and Izzy to think they were in the comfort of their home, to be surprisingly greeted by a naked woman (even with undies on, I call it naked -- if it would not be accepted attire on the sidewalk, it's naked), and than have that person pee in front of you.
Bottom line, they all got off to a rocky, uncomfortable start.