Hi,
It sounds like you are on the right track. It is a good idea to keep her confined until she is calmer. If you have an old t-shirt or other clothing item that you can put in the cage with her that is a good idea. It helps her get used to your scent. Move slowly and talk quietly around her. Sit by her while she eats so she can get used to you being close to her. Use food to try to get her to come to you. Tasty treats such as canned food or even catnip may work well for this. Taming a formerly feral cat takes lots of patience. I have done it before, and food really seems to be the key. Once she is taking all of this well I would let her move into a larger space, but not the whole house at once. I would probably keep her confined to one room, and then do all the same things over again until she is coming to you in the room and seems relaxed. Keeping her confined to one room will also help with litter box use as this can sometimes be a problem with cats used to being outside. Here is a link to a page with a little more information and a success story:
http://www.geocities.com/Heartland/Pointe/9322/taming.html
Its wonderful that you are helping willing to put the time and effort into giving this kitty a home! If you have further questions let me know, and I'll be more than happy to help. If this answer is helpful please click accept. Thank you.
Lynn