I'm afraid that I can't be of much help, as I am going through a similar situation with my daughter. At least, you know you are not alone!Do you know the actual results of your daughter's stim test--how high her cortisol and 17 ohp rose? Also, how long had she been off of steroids when the stim test was done? If her adrenals had shut down, it should have shown up in her cortisol levels on the stim test. Also, if she's been sick or under physical stress, she probably would have shown signs of an adrenal crisis.
Also, when they do DNA testing, they do not usually check for ALL the possible mutations, but for the 12 or so most common ones, which do account for about 90% of the cases of 21 hydroxylase deficiency. So it's possible that she has one of the rare mutations. Or that she has a different form of CAH, such as 3 beta.
Last year when my daughter was a senior in high school, she asked me if she could have ADD. She felt like she was having a lot of trouble concentrating in class, staying focused, etc. She can read something and then have no idea what she just read and she always complains about her memory. I've never had her tested, though, and she doesn't have lack of motivation. She struggles along now in college, and has to take a lighter load than others because she needs a lot of sleep and is still tired all the time. Hope this helps a little.
