I would think about bumping up the hot hide temps to 92f and trying some kind of water softener or bottled water.
But the above depends on the following answer - what do you use to measure temps and humidity and wherabouts in the tank do you take the readings?
dr del
To add to this, and I apologize if it's a dumb question, but how do you know she's impacted? Could it just be the sausage butt that they get right before passing urate/feces?