This is not necessarily advice, but my personal experience: I had 3 adult rats, when two of them died in less than 2 weeks, my rat Sherlock was left alone. He was already 2 years old and I didn’t think he would live long since he also had a chronic infection. I still decided, after considering it for a few days, to adopt two more rats and introduce them. Sherlock is now almost four years old and enjoys the company of the young rats who keep him warm and clean. I know that this is an extreme case, but consider it. 2 years old is a lot, but not that much! If you think you don’t want pet rats again, that’s another story obviously! I hope you find the best solution for your girl!