Got her xrays today, thank you everyone who donated or bought something to help me pay for it. Unfortunately it seems she has a cancerous growth on her knee and the only option is amputation, which my mom does not want to put her through because it would be very stressful and the growth is likely malignant so amputation may still be ineffective. For now she seems fairly comfortable when you don't touch her leg, she is eating fine and seeks out petting, purrs and gets around okay without putting weight on it, so we are just going to let it be. If her condition deteriorates and she is in pain then we will put her to sleep at that point.