Hi Bumbleberry! Yay, a fellow holland lop parent
At that age of 6 months, I would say her toilet mistakes are caused by behavioral changes (blame it on those raging puberty hormones)! She is simply maturing and doing what bunnies naturally do– marking territory and distinguishing their areas. If she is doing it right beside her litterbox, that actually isn’t so bad; before he got neutered, my little buck used to leave puddles here and there outside his hutch at any point during the day!
As you probably know already, there is absolutely no use trying to reprimand a bunny to make him/her understand the way you would to train a dog. SO, the best way to try to help your girl resume her litter habits is to wipe up the pee with like a paper towel and leave the paper towel in her litterbox. They can’t help what the hormones dictate them to do, but they are still very smart. It helped my Teddy after all, I don’t think he liked me invading his space without his consent
Try that and see if it works for you too, and good luck!