Qu. for parents of shy kids?

My daughter is 4. She has been really shy since she was 1. She does not like anyone she doesn't know. There is some friends of ours that she has known for 3 yrs that she hates. They are more then nice to her, but she doesn't know them well. She is only ok with people she knows well. Family and the such. She does seem to do better with women then men. We put her in a preschool to help with this before she starts school next yr. It went very well. There were moments but for the most part she has adapted well, and made friends with her teachers. There is a new teacher that started a few months ago. He is nice. I've met him. He's not her teacher but will sometimes relieve her teacher for lunch and watch the cl for about 30 mins to an hr. She has started having problems. She HATES when he comes in her cl and starts crying. She swears he has been nothing but nice to her but "I don't like him b/c I don't know him" That's what she told me. I have tried everything I know. Any ideas?