How Do We Help Our Cat To Adjust

by Sue

We adopted an 8 year old cat, from her original family, whose young son developed an cat allergy.
We brought the cat home and she has stayed hidden for one week now. She came out from hiding after two days, but stayed about 5 feet from us. When she did come closer to rub our legs, we petted her and she hissed and nipped. Now she won't come out from hiding at all. She is eating and using her litter box, but we are concerned for her health and adjustment. Are there any hints for us to draw her out of hiding? Should we force the issue? This is not what we imagined would happen. Thanks for any advice.