Ladies please help me!

My boyfriend moved in with his two cats. They are chilled and happy. Mine are hissing at each other. The girl attacking the boy. Never before, they groomed each other and loved each other. I am trying not to stress so they don’t sense it. I was told to separate them for 24-48 hours, but I only have a bathroom. The girl is in the bathroom, but I feel guilty. I have gone and spent time with her, them out with the boy. Help! Is this right? I cantlet their confusion turn into anger towards each other.