Welcome to BinkyBunny Fanman!
The first thing you should take care of is finding out if she is spayed or not, in addition to really helping out with the litterbox habits, spaying reduces the risk of cancer in your female bunny, and ovarian cancer is very prevalent among female bunnies – so it will keep her healthier as well.
The reason may be the cats, she probably wouldn’t want to go in there if she knew a cat was in there as well. I had two bunnies that really like to pe next to their box because they were actually trying to mark the corner of their cage, so I got them a bigger litterbox and now they use it all the time. Is where she is peeing now a corner or a room? If so, try moving the litterbox to where she is peeing, or try getting a slightly larger box that will cover the area where she is peeing.
Generally you wouldn’t have to clean out a bunny’s litterbox twice – what kind of litter do you use? I use a pelleted litter, and I clean out my bunny’s litterboxes twice a week. Do you have a layer of litter and then a layer of hay on top of that in the box? Also – is the litter you are using cat litter? If it is cat litter that may be another reason that she won’t use the box. Try a litter like “Carefresh” or “Yesterday’s News” which you can generally find at pet stores (do not use pine shavings!). Also, “Feline Pine” could work in your bunny’s litterbox.