Definitely not bad at all. I rescued one female who was 780g at 3 years old. She was being fed one mouse twice a month.

I would start slowly with her and try one small, weaned rat once per week. The rat only needs to be around 40-50g. See how she does on those for a few weeks, and if she looks like she wants more, give her a second rat the same size(right after the first one on the same feeding day).

I also would get her checked for internal parasites, just in case. Take a small sample(teaspoon size) of her fecal matter and place it in a ziploc baggy, then refrigerate it until you can get it to the vet(preferably within 24 hours, but up to 48 is fine).