I am so sorry you are going through this. My girl ruptured both which can occur when the first one goes and is unstable causing the other one to blow. I would definitely head to the orthopedic surgeon for a consultation/second opinion. You do not want to wait until she ruptures the other one or arthritis sets in.

My baby had a double TPLO at 2 years old. Back then it was fairly new but I felt the best option for her. As it turns out this procedure is now the gold standard. She was never as sound as before but her xrays 6 years later showed no new arthritis which really impressed the surgeon. It is a major operation and a slow recovery but we were very happy with the results and I would do it again without hesitation in a healthy dog.

You will need to prevent her from licking the incision even if it means wearing an E collar 24/7, infections that reside under appliances (the plates) can last years. As with humans the rehab period is crucial so you will HAVE to keep her quiet no matter how much it makes both of you crazy. Frisbee and chasing squirrels are very common ways of blowing a knee so I'd really try to modify her activity. Perhaps take her swimming and toss the frisbee in the water rather than doing it on land.

I'll send good vibes your way and feel free to pm me if I can answer any questions. Hugs, Jules