Repost about a shy child?

I'm reasking this because I didnt get a lot of answers the first time around. Any info would be appreciated. Thanks.

My 4 yo daughter has been attending pre-K for 2 1/2 hours a day (1-3:30) since Thursday of last week. Before classes started, she was very excited about going to school and kept telling us she wanted to go to school, make friends, etc. Yesterday, her teacher asked me if she talks at home. I told her she does, most times we cant get her to be quiet at all. She asked because my daughter has not said anything at all to anybody in school and when the teacher asks her to do something, my daughter only smiles at her and doesnt do it. Shes not a defiant child, she listens to me and her dad. And she doesnt have a hearing problem. I was shy when I went to pre-school when I was her age, but I dont remember being shy to the degree that my daughter is. Im not sure if she will get used to it and start to open up more but I hope she does. Is there anything I can do to help her be more outgoing or to at least listen to her teacher? I talked to my daughter about the importance of listening to her teacher today. I explained that me and dad are happy that she listens and helps out at home, but when shes at school she has to listen to her teacher. She didnt seem too interested in what I had to say though. I plan to keep working on social interactions and whatnot with her but what are some good techniques to bring her out of her shell?