Hell yeah it's a good sign! A Dub rarely hears about what critical thinking is, and would rarely think it is useful to them. Just lay off of doctrinal issues and science altogether for a while.
If she says she feels her mind is turning to mush, that's because it is. I remember exactly the feeling you described earlier. Describing logical fallacies is good, a list is better. There are a few good YouTube videos that actually show them being used. I found that to be the best personally.
It might just be wishful thinking, but if she once again feels intellectually empowered she might even allow herself to see the bullshit in the pages of the WT. if you jump on it too hard, she might see your motives and back off the whole thing. This could be a great opportunity!