Litter training

I have a question. Is it ok to use kitty litter in Rabbit cages. Cause i've heard things saying you can and can't. My rabbit Iris had pretty much gotton the hang of it but then my sister accidently hit her cage while she was in it and ever since she was afriad to use her litter box. So we bought her a new cage (she needed a bigger one anyways) and a different color smaller litter box (cause she just liked to lay in it and not use it.) She had to get used to the new cage, we got one with shelves and she loves to jump up and lay on them. She uses the potty to pee in but she still leaves poo around the cage. I have laxed potty training for a few weeks while my boyfriend are away for summer school and only come home on weekends, I think she's having seperation issues and not using her potty so I gave up tilll we're back at school full time. She's getting spayed in a couple weeks too so hopefully that will help. (But she really won't be happy with me). Is this ok to let loose for a couple weeks? Or should I tell her babysitter to keep at it while we're gone. I hope she doesn't permantly hate me for this but I feel soo bad for leaving her and it was the only way...

DON'T use clumping cat litter in the tray like clay litter, as rabbits like to nibble whilst they're pooping! I use wood based cat litter in my rabbits trays, you can also use care fresh, a recycled paper litter!