Dora had her 1st puppy school last week, and was just the same, not really scared, but incredibly shy. This week was a little better, and she sniffed a couple of the pups.
At home with Bailey she is a different animal. Bailey did the same puppy school several months ago, and he was 16 weeks when we took him, he fell in love with the place, it was the high point of his social calendar for the 6 weeks, and he made loads of friends. Dora was 12 weeks. I think age has a lot to do with it, and like you I have given up on the training bit really focusing on the socialising, which she so obviously needs.