First things first - I find that birds when they have a really dreadful molt like that get anemic way faster than normal, and they get flat out sick. their immune systems are most definitely lowered, leaving them more susceptible to other things.
If this were my hen, this is what I'd do.
First, I always eliminate the possibility of nearly microscopic parasites - lice and mites. Lice you can check for during the day, mites take more effort as you have to check at night. It might be that they've been on her and left, leaving her in an anemic state.
Second, evaluate her diet. Where she is now, she needs daily vitamins, a completely fortified supplement age appropriate that has additional protein. For molting hens, I really like gamebird feed which isn't surprising as I like gamebird (not gamecock) breeder/layer for my laying hens. She needs all the calcium she would for laying because calcium is required for feather building. SO is protein and also fiber. So a complete feed is in order. She could also benefit from a week's worth of daily vitamin supplementation as she's not taking this in stride. Her immune system will need the boost of an oil-based (not water based) vitamin supplement that has a range of vitamins. I like NutriDrench for this, or polyvisol baby vitamins (without added iron, see the vitamin section, oddly not the baby section, of your local drug stores).
I would also make sure that she gets probiotics of some sort daily to help her system deal with the stress. Yogurt, acidophilis capsules, Probios powder, just some live bacteria.
As for the quills, YES they hurt. Imagine wooden pencils poking through your skin, without the benefit of the slick paint, and there you have it. That and hormonal changes, and the body needing more than it usually does. So think pencils through skin while PMSing while fighting a cold. YAY!
I'd keep her in a warmer place because of her feathering. I'd avoid feeding her grains, just a high protein feed. Give her oyster shell as usual, and clean water, the vitamins for a week, and maybe even a little egg twice a week to help those feathers coming in.
I think that if you give her that starting tomorrow, she'll perk up for you. Botulism, she wouldn't be alive right now, and she would be excreting feces that were very runny and unbearably smelly. She wouldn't be able to hold up her head. So that's good news. I think we can get your hen through this.