You didn't say where you're located, but if you are in the United States, you can post her at both of these web sites to help locate an owner:

http://www.tabbytracker.com/

and

http://www.lostandpound.com/index.php

Please be sure to get the new kitty FIV/FeLV tested before letting her out with your current kitty.

Good luck and thank you for taking care of her.