When Grant came back after Lisa had sex with Suzy, they didn't talk to each other, suggesting that Grant has some difficulties accepting it. I would not be surprised if his behavior yesterday had something to do with Chloe sleeping there.
The interesting thing is that Lisa is the one who is deciding. Grant is too weak. It seems to me that her goal is to stay in VH as long as she can and if that means having sex with girls or even doing more than that, i'm sure she will do it.