We all deal with relationship issues. If you were married or had a partner and you all decided to seperate but remain living together, would you allow him / her to bring another man / woman into your home?
Nope, I wouldn't expect to do it or have it done to me. That is extremly disrespectful. On the other hand if it turned into a long time of roommates and you both were going on with your lives, there might have to be compromises made.