hi hiphop – welcome to Binky Bunny!
I am so glad to hear you already made an appointment to have her spayed – that’s fantastic! It should really help.
If she’s made a nest, she is experiencing a false pregnancy. It would explain why she’s suddenly gotten more aggressive. Basically her body has tricked her into thinking she’s pregnant. It is not medically harmful in most cases, but it is very stressful for bunnies. Once she’s spayed, they’ll stop fortunately.
you’ll want to keep a careful eye to ensure she doesn’t get seriously aggressive and hurt him. If you’re seeing serious biting (nipping is ok) or vicious chasing, you will need to separate them. I sincerely hope it does not come to that. Also – if he starts to hump her face, you’ll want to make sure to turn him around. Bites on the boy parts are very dangerous and scary!
Also, you’ll want to bring them both into the vet when she goes in for the spay (provided they’re still living together). It will be a great comfort to her, and some bunny bonds are broken when one comes home smelling like the vet. So, it’s best to bring them both in.