Need help for Shelby's second ACL surgery

Earlier this year, in May, Shelby and I were playing frisbee in the park when she suddenly cried out in pain and then stopped putting weight on her right leg. I took her into her vet and they diagnosed her with a torn ACL and we were told she would need surgery to repair it.  The surgery was $3000, during this time I paid all that I could and had to finance the rest through my credit card but I had the ACL repair done. The doctor said the chances of her tearing the other side were high and looking at her xrays it was very close. It's been 5 months later and I let her in from her normal morning potty routine and sure enough she had stopping putting weight on her left side. I took her back to her doctor and he confirmed the left side is torn and another procedure will need to be done. The estimate for the procedure is between $2900-3700.  I am still paying on the first ACL repair and I just finished paying off my student loans and am not able to do anymore financing for the second surgery. Shelby is a Golden Retriever and she just turned 8 on November 4th. She is in excellent health otherwise. She is just an active girl who loves playing with her toys, and frisbees, and her little sister Charlee. It hurts me to see her struggle right now. She is on pain medications in the meantime while we figure out how to pay for her procedure but I don't want her to be in pain anymore. Shelby and I will be beyond grateful for any of the help we can get.