PATIENCE
When little ones come into a new situation they are scared and they need to be gently handled and kept in a quiet situation until they become more comfortable with you. No sudden moves and spend time on the floor with her coming to you. It would help if you had little treats so everytime she came to you she would get a reward. I would not take her out to new situations or crowds until she learns to trust you. Keep everything low key and soon she will become more relaxed.
How much do you know about Yorkies? Pet stores have a book called Yorkies for dummies, that would help you.
Your little girl should be feed twice a day and it should be very good quality food. Have you taken her to the vet for a checkup yet? How old is she?