She not only slapped him once but a couple times and tried kicking him. I think you have to do an awful lot to get kicked off these shows anymore (see this year's real world season epic fight) which is sad and somewhat unsafe.
I have read online that a lot of times those houses they put them in for the challenge look beautiful but really don't have the capacity to hold 20 people (3 or 4 showers/toilets). It creates a lot more tension and with all the booze they give them adds fuel to the fire. In the early ninja scene tonight, everyone was sleeping in the room with pool table, I wonder if its the only ac room? That would get old fast and make any same person a little crazy.