How to help 2 year old

My 2 year old has always been on the shy side ever since being a baby! If anyone else would look at her she’d cry and cry. She now attends pre-school 2 days a week for 3 hours at a time. She speaks very clearly to me and close family members but she won’t say a word at school!!! She loves the school and I wouldn’t change the school she’s at! The staff are amazing and so patient with both me & her. She always comes home and says “I love school” or “school was fun” etc etc. She’s the same if she’s not seen say my mum for a couple of weeks it’ll take her a good 1-2 hours to warm up to say anything at all! Not one word will be spoken! I’m so concerned about her social-awkwardness. I always thought I put it on her but I’m very open and quite polite and chatty with other people including strangers! I don’t know what else I can do for her! I take her out often, we go to toddler clubs on other days and then the days I work she stays with her Dad (my husband) so it’s not as if I’m leaving her with a stranger. Someone please help! I just want to help her not feel shy or awkward and I know school would love to hear her speak!