Female dog in heat and male wants her.?

I have 2 8 months chihuahuas, Bruno and Princess. Princess is in heat. Bruno wants her lol. I have them both in the crate with a divider so they wont get to each other.Will that keep them away from each other? also they are home alone all day. I tie one at one end of the garage and princess at the other end LoL. They are Brother and Sister. They are both getting spay and neuter next week. what else can i do. vicks on her butt doesn't work.