There are many products that work well for arthritis. Lintbells makes a product known as Yumove that can help it just takes a bit to be effective. Adequan injections have helped many old dogs. If it's getting close to her time, you can see if there are any hospice care veterinarians in your area that can provide pain meds to help improve a bit her quality of life. Many will come to your home. Several vets will also come to homes to put a dog to sleep when the time comes. There are also mobile vets. I am so sorry it's heartbreaking for sure.