How much longer can she survive?
I have no idea.
I would certainly keep offering her the dampened chick starter, since you say she ate some of that.
Animals (and even people) can live a long time on a diet that is not perfect.
The first, most important thing is water (any liquid.)
The next most important is calories, and all the things you mention have some calories.
If other things are lacking (protein, vitamins, minerals) you will eventually start to see deficiencies, and finally death-- but it might be quite a while.
A chicken that is growing, laying eggs, or molting has much higher nutrititional needs than a chicken that is not doing any of those things. Since many female chickens grow, then lay eggs constantly except when they are molting, it is very important for them to have a good diet. Right now your hen is not doing any of those things, which means she can go longer before bad effects start appearing.
If you want her to keep living and stay healthy, you should try to get her back to an appropriate diet, but it's not something that MUST happen immediately.
she is back to liking corn and a few peas but warm soggy bread - hand fed - is by far her favorite. How much longer can she survive?
Soggy bread might not be too bad, depending on the bread (whole grain bread being better than white bread, for example). And if you can use something nutritious like egg yolks to make it soggy, that could also help. (Egg yolk is perfect for the first few days of a chick's life, and is pretty good for chickens of any age.)
I would try offering some warm soggy chick food, hand fed, and see if she'll accept that instead
