Amanda,

Try wrapping her in a towel with her only her head showing and gently pet her, whispering to her. If you can't get her to come out from under the bed, just lay on the floor and give her treats, gently whispering to her and slowly blinking your eyes. This will let her know that she can trust you. Once she knows that you mean her no harm and are her source for food, she'll start trusting you. Try not to scare her by making any sudden moves.

It sounds like she could be semi-feral and possibly abused. It's going to take lots of love and patience, but I guarantee you she will come around.

Feral and semi-feral cats don't trust humans, thanks to irresponsible people who toss cats out like trash. It forces them to fend for themselves and not trust humans.

Good luck and keep us posted.