How do I get my cat to play nice or stop crying all night?

I have three cats. Two are mine, one is my husband's (Peanut). I've had my two cats for a year and they never had a problem sleeping apart from me. However, about a month ago I noticed one of my cats (Tripod) would sit outside my bedroom door and cry all night. I figured she was lonely so I would leave my bedroom door open and let her come in. But then Tripod would come in, upon jumping on the bed, she'd swipe at Peanut and hiss and keep trying to get some punches in. Then she becomes so fixated on Peanut, she won't sleep or even pay attention to me, all she wants to do is fight him. This is new, like I said I've had her for a year and even when Peanut moved in months ago, she had no problem sleeping in the living room while he was on my bed. My husband refuses to kick Peanut out and it's annoying as well as heartbreaking when I hear my little Tripod cry like that. How do I get her to either play nice or stop crying?