Removing Celeste's Tumor

My beautiful rat Celeste has developed a large mammary tumor next to her right back leg. It has grown to almost the size of a golfball and drags on the ground. It will soon begin to impede her movements and will decrease her quality of life significantly. I am not able to work at this time because of a chronic medical condition, so I have no way of paying for the procedure to remove it. Celeste is my companion animal and is very important to me, she is only a year old and is very healthy otherwise. She has 2-3 more years of life, and I cannot allow a tumor to consume her. Please, please help me save my beloved rat, she is the light of my life.