Hello Stacie & Puff!
Are you able to clean up the pee as soon as it gets outside the litterbox? If you spray it with vinegar it is very easy to clean up. The reason I ask is because maybe Puff now thinks that she can pee anywhere because she’s been doing it for awhile. Try cleaning up the pee right away, but before you clean it up, get some on a cotton ball and put it into her litterbox to remind her that is where the pee goes.
Also – what areas of the cage is she peeing in? Is it the corners of the cage and in her house? For some reason I have noticed that bunnies like to pee in corners of the cage, and if that is what she is doing, you can try adding another litterbox to a corner that she frequents. Did you change the litter at all? She might now like the new smell and avoid the litterbox also.
What kind of diet does your bun have? Did a friend come to visit you that had a pet? Did you give your bunny any new items in her cage? If you can give us a little more info on where she pees around the cage that might help.
I hope that we can help you fix this 