I agree with both
@Nijn and
@Preitler that your rabbit will need to see a vet, or the condition will likely get worse. If she is acting like she is in pain, she probably is unfortunately.
Taking care of a rabbit is a lot of work, and that includes finances and research. Even with rabbits who are in perfect health, the owner will very soon spend more money than what they originally got the rabbit from buying monthly supplies. I remember you mentioned in a different post that you believe rabbits are better off being alone as well, so I really encourage you to read further into recommended rabbit care and see what you can and potentially cannot provide. It's never comfortable thinking about or hearing this (especially from a stranger), but a lot of stress for both the owner and pet can be relieved if the decision is it's best to re-home to someone else, that way the owner isn't responsible for something he/she cannot manage at that point in time and the rabbit can get proper care.
If your rabbit does have syphilis (unsure because the pic isn't posted yet, but speaking hypothetically) and it is now symptomatic, it requires medical treatment from a vet, meaning you would need to purchase medication for a minimum of 21 days. Price will vary vet to vet, but I spent $105 on one of his syphilis medications, and had to give it to him via a shot in the back every day. To know what exactly your rabbit is suffering from and what medication/treatment is needed, she needs to see a vet, and yes, that will cost money. What is your budget, if you don't mind sharing? Sometimes gets let you pay in installments.
It's good that you're being observant of her behavior and you are trying to get a good look at what's going on, but it sounds like you'll need some professional support for your rabbit and to do some research on your own about rabbit care and costs.
