yesterday I got this gorgeous white bunny and the bottoms of her feet are pee stained dark yellow

. Is there a way to get rid of that grossness? I don’t understand how people let this happen so often, isn’t it preventable by using appropriate litter?
I wanted to include a photo but can’t figure out how.
I'm so glad you figured out how to add the photo because she is gorgeous! I love her long sideburns. I agree with most people who've responded to your question in that if you keep her area clean, her feet will gradually get better over time. I've found the majority of rabbits want to be clean, and will keep themselves spotless as long as you're doing your job in keeping things up.
If the stains bother you, though, I would suggest doing what I have done with some of my bunnies when they've gotten into a mess on their bum. I take a round, plastic basin and put a few inches of body temp water into it. I then put a cloth on the bottom of it and pick up the bunny, holding them close to my body with one hand holding the front paws, and the other holding the big, back feet. I slowly dip their toes into the water and gradually set their feet on the bottom of the basin. The whole time you can be kissing the top of her head and speaking to her in a low, gentle voice. If she's calm and not struggling to get away, you might be able to place her front paws on the edge of the basin's rim. (It may take a few times of doing this before she'll let you do that without struggling to get away.) You need to stay very close to her the whole time because they are very fast and she could make a big jump and spill the water and possibly hurt herself. I've found they all love to be kissed and snuggled while this is going on. Depending on the bunny, you can put the basin on a counter or table, but to be safe I always do this whole procedure on the floor - that way, if they do get out of your grasp, they are already on the ground. (Bunnies can easily flip onto their backs when they fall and can be seriously injured when falling from a height.) When they have a messy bum, I let them soak in the water a bit, then slowly swish the water around that area. If it's really bad and there are hard pieces stuck on there, I will gently keep checking and sometimes have to use my fingernails to break the pieces down into smaller ones. Eventually, the warm water and the action of swishing the water will loosen everything off. Sorry that this is so long, but I just wanted to describe it as best I could to someone who has a new bunny and might need this info for other problems in the future.
It would be more difficult to get at the bottom of her feet this way, since they are resting on the bottom of the dish, but if she'll allow it, you could lift her slightly off the bottom of the basin and gently rub the bottoms of her feet. I think you'll find that the clean, warm water helps get rid of anything that could be attached to her. Be very careful taking her out of the bath. Lift her straight up, and take her feet into one hand so you can squeeze the excess water out of those big thumpers. You can then place her onto a towel you've previously laid out on the floor beside your basin. Hold her down onto the towel with one hand while you wrap the towel over her with the other. She will probably be doing her best to get away from you, so be ready for a fight! At this point, your back is probably aching from leaning over her and the water, so you can go sit in a comfortable spot and give her more kisses while you gradually dry her one area at a time. When you rub the bottoms of her feet with the towel, this will get even more of the pee off.
Well, I hope you didn't fall asleep through my exceptionally long answer, but I just know that when I'm looking for help with the bunnies I need details. I hope you get some use out my answer. Good luck with your gorgeous girl. I think Rapunzel is a great name! You could also go with Mrs Whiskers or Spot.
Note: I just use plain water and while I use diluted vinegar to clean their pen and litter boxes, I try not to use anything directly on them. I have used cornstarch to get poop off their fur if it's really cold and I don't want them to get wet. Some bunnies will allow you to use a blow dryer on the cool setting to dry them, but depends on your bun. Cornstarch does work well for poop - it slides right off the fur, so could work for the feet. I discovered this when I read that it takes stains out of rabbit fur on clothing.