I just read the other day I am discouraged to post here, but wanted to give you some hope nevertheless. I can’t tell you much about the particular prognosis for your daughter. In general they can vary greatly and I think it is important to keep in mind that, even when it doesn’t look too good, they can be proven wrong. My own prognosis wasn’t too bad, (those were pretty much the words I got from my psychiatrist, he didn’t mention any particular things that I could or could not do) certain circumstances favored a good outcome in my case. Others on the forum have been told they’d never be able to do this or that, and still, perseverance, therapies and the like have made them achieve many of such things.
As for mental decline… that term covers a lot. I do have less initiative, motivation in general is an issue, and became less talkative, these things developed over time for me, some starting before, some after my diagnosis.
I am in university, and was so as well before the onset of schizophrenia. My grades have slightly increased over time, when compared to the period prior to the onset. That aspect of mental life thus seems not to decline for me. But, I was diagnosed only three years ago, I can’t tell how these things turn out in the long run.
Things like difficulties with concentration and memory may or may not be temporary, I can only give you my personal experience with these issues. Nowadays my episodic memory isn’t as good as it used to be, but doesn’t really cause me any trouble. I had an episode where it took me half an hour (literally) and all the concentration I could gather to make a sandwich. I just couldn’t figure out what was supposed to go where etc. This got much better after a while.