To chime in quickly.
Mediums are probably too big. At 2.8 pounds, I would be feeding small rats. Yes, they can eat a medium, but it's a big meal and will often cause them NOT TO EAT. Small rats will probably allow growth, but also keep her wanting food and HEALTHY.
Defrost properly (ask if you don't know how), keep cool side over 78F, feed at night with the lights out or dim because that's when they normally hunt.
Get a heat gun, yesterday, and thermostat that controls all your tanks, or one for each if you don't have one.
Do not handle until she eats 3 meals for you.