I had one like this, a very finincky eater. She only ate mice, long after my other girl went to rats, and she ate them without much sense of urgency.
I feed frozen thawed from rodentpro.com, and have had great results with their product.
One of my girls has a fantastic response, she attacks and constricts dead rats within a minute of them hitting the cage.
The other remained a mouser forever, I just recently got her on rat pups by scenting their thawed bodies with mice bedding and dangling them in front of her instead of just dropping them in. She's had 4 in the last week. Thank God, she was on quite the fast and isn't near big enough for her age (a little over a year old), I'm very glad I've got her on rats now, I've seen first hand with my two that the rat eater put on size very well after switching over from mice.
I toss the frozen rat in a plastic cup full of hot tap water and leave it for 10-15 minutes, until fully thawed out. Then I dry them off a bit and toss one in with Muffin, the destroyer, and the other one I scent and heat up a bit more with a heat lamp for Bagel, the Priss. Then after a minute or so of dangling in front of her hide hole, she snaps it right out of the tongs.
It can take some work getting these things to eat, I was worried for a while I was going to have to start breeding ASF's or gerbils to get Bagel to eat right, but I've got her straightened out now.