We had a male with the same issue and joked about him eating "popcorn chicken" every week, except is was four mice and not six. This is how we got him switched and he's a happy rat eater now, though he still wants live over f/t so we will work on that next. It took about a month for the transition.
Start with 4-5 mice and a rat weanling the same size as the mice. Note that larger rats will kill mice, but a weanling likely won't. Keep the mice and rat weanling all together in a large critter keeper for an hour so the rat smells nice and "mousy" and the mice pick up some rat scent. Offer one mouse as normal, maybe two, to get her into feeding mode, and then offer the scented rat weanling and see if she takes it. Once she's at the point where she takes one rat per feeding then offer four mice and two rat weanlings or a one slightly larger rat. After a few weeks we started offering the scented rats first. Once our guy took those readily he switched to unscented without any problems.
Wow thats a great idea, i will definitely try that, thanks