To answer your questions...
1) Yes, she would be a candidate especially if she can't hear anything now.
2) Since she had hearing previously and has developed speech and all that jazz, she would be an excellent candidate.
3) Being totally deaf now would not hinder her chances for having a successful CI.
The likelihood of success with a CI is as follows (in order of probability to be most successful to least successful)...
1) Had hearing and have developed speech sufficiently (typically by 5 and older)
2) Receive a CI very young say 1-5 years
3) Been HOH and developed speech (this is my category and I'm a smashing success)
4) Been HOH and could hear sounds and not understand much speech if any
5) Deaf and really never heard sounds let alone speech
Remember just because one is a better probability category doesn't mean one will be successful. The best attitude is to keep expectations low and be pleasantly surprised.
I agree 100% with your statement about "high hopes, low expectations." That's the mantra followed by all CI users and following that advice really does work.
When I went into my activation day, I approached it with a sense of adventure. I didn't expect that I'd be able to understand anything I heard -- including environmental sounds. To my delight, I heard all kinds of environmental sounds which made me forget about the fact that I couldn't understand speech.
Even throughout the following weeks, I took things slow and let sounds come to me. For example, when I watched TV or listened to the radio, I relaxed and thought about the words or voices I *could* understand.
As for the categories above, I fit under #1 and #3. Why? I was diagnosed with a mild hearing loss at age 3 -- although my HA and CI audis believe the loss may be congenital due to the fact that newborns weren't given hearing screenings back in the late 60s/early 70s.
After having my first CI for 2 years and my second for a year, I'm now able to understand 97% of sentences in quiet bilaterally, 93% of sentences in noise bilaterally and 99% of sentences in quiet with my Freedom (with my N24 I understand 54% of speech in quiet which I attribute to it being older technology).
Granted, I'm totally blind and always grew up using my hearing, but even if that weren't the case, I suspect that my chances of success with a CI would still be good to excellent given the fact that I've had over 20 years of auditory input.