I belong to the Guinealynx forums and will tell you that is the best site for guinea pig owners. I also have a small rescue here in NW PA. On the site you will be able to get help finding a vet that is more cavy savy. In my opinion, it sounds like tumors on the lumph nodes and if she is eating and drinking, they may be benign. I do think you need a better vet. Please don't rush into Euthanasia.
http://www.guinealynx.info
Great site for all things guinea pig.
They say average lifespan is something between 5 to 7 years.
I had three. I must have bad luck because mine died at the following ages: 2.5, 4, 5.5
healthy guinea pigs live from 8-10 years i had alot of pigs growing up and right kno i have 2 baby pigs there both 1 and ahalf months old
Guinea pigs usual life span is between 5 to 6 years. It is not only the will to live, that you have to take into consideration when considering the option of euthansia. You also have to weigh in her quality of life. Is she in any pain? Is she still playing and enjoying life? Does she still have a healthy appetite and is her fur still silky and beautiful? We have to be the advocate for the family pet and make decisions that is in the best interest for the pet. Sometime when the pet is suffering, the greatest gift that we can give them is a relief from their suffering.
However, if your pet is not suffering and is still enjoying life, it may not be time yet. Guinea pigs have common skin tumors which appear as solid bumps over their lower back. These can grow quite large yet are benign. Your veterinarian can determine if the tumor is cancerous or not. Some vets can also remove the tumor but you will need to discuss the costs as well as the prognosis with them.
Although you veterinarian may be correct in advising euthansia for Nillie since she has reached her expected lifespan, you may still want to get a second opinion from a cavy expert. Call around for an exotic specialist or breeders in your area to see what your options are.
Good luck,
Dr. Youkey