Once completely thawed, I just leave in hot water (hot hot hot, the hottest we get from our tap) for 10min.

Always gets warm enough. Sounds like she's just not used to thawed yet. When she coils, keep a hold of the rat still, and wiggle it while she's in the coil. Fast at first, then slowing down, simulating a dying rat.

That always got my baby balls going on thawed if they had any problems.

Keep trying, and good luck.