I had a rescue who came in at 3 years old and 780g gain approx 1500g from May 06 to December 06 on 3(sometimes 4 if I had an extra) mice a week. It's normal You should see about a 100g+ weight gain per month.

She's now about 5-6 years old and 2400g(and gravid with Pastels for the second year in a row).

Good luck with her! And believe me.. Mice get the job done just fine.