Save Vanilla: Urgent Surgery Needed for Sweet Guinea Pig

Hello, my name is Tina. I have a guinea pig named Vanilla. She went to the vet last month because her nipple was swollen and bleeding. The vet said that she would need antibiotics. Vanilla took her full round of antibiotics, but the mass on her nipple is still there and has been consistently bleeding for the last month. Her cage mates are so scared and try to protect her whenever I try to give her the pain meds that she needs so she won't be in pain. Vanilla needs surgery to remove the mass since the antibiotics did not work, and it will cost around $800, which I cannot afford. I don't know what to do. I don't want to lose my baby. She is the sweetest girl you will ever meet and will lick up your tears when you are sad, while looking at you with comforting eyes. When I look at her, she looks at me as if she is asking for help, and I don't want to lose her. She's only 3. This is my last resort; please, anything helps