I find 18 months is the turning point when you start to see a child move to the next developmental level that includes language and socializing which is also part of following instructions to a certain extent. A lot of what kids do before this point is learned responses like we put shoes on after snack.

She may just be very shy since she is with the group so little. More doctors are doing more thorough exams including developmental checklist at the 18 month check up. I let the one I have go to this point hoping the doctor would say something to mom and he did. She is now being monitored and will be reassessed in 3 months.