It’s not old age, old age is not a disease, aging is a normal process, and this is not normal. She needs to see a vet asap. She could have what is known as a rabbit cold. In rabbits, colds are bacterial. They can progress down into the lungs and cause pneumonia. She would need antibiotics and sub Q fluids and a painkiller. There are also decongestants and broncodilators a bun can have. To help her appetite a gut motility drug can be given if there’s no intestinal blockage. Rabbits often hide symptoms of illness really well and when the disease manifests, it’s often first in the form of inappetence.

To help her breathe you could sit her in your lap and run up a good steam in your bathroom. 10-15 minutes of this could help her breathe better.

That she peed on the floor was probably because she can’t move very well. There are other conditions beside a rabbit cold that could cause this, for example e cuniculi that can affect for example the heart and the nervous system, often resulting in the bun getting temporary hind body paralysis. You can’t know without a vet exam.