My child has strong people anxiety

I'm starting to notice my girl is different from others. If another child takes her toys etc she'll let them even if she really wants it. Her friend tried to play with her the other day and said rah, she ran back to me. I take her to groups but if her group leader talks to her she gets upset crying and clings to me. It takes near to 2 hours for her to start to relax around people. If she gains as certificate I go with her to collect it, no other children need this, obviously I'm her mum happy to do but I'm getting worried as younger kids are much more confident.