she is just shy. What you might try is adding some rescue remedy to her water
http://www.rescueremedy.com/ The shelter that I volunteer at uses this regularly in their cats water- it calms the felines down some. You can buy it at Petsmart or other pet stores. I am just amazed that she was so social at the pound, usually it is the other way around. And in my experience, calico's and torties tend to be more shy and skittish than other breeds. You might also want to post this on the pets section of DU. Good luck!