What your child exhibits are typical behavior associated with an introverted child. This personality type gets exhausted or drained with public interaction and needs to be positively encouraged to have public interaction. What will certainly help is to have a dry run at home with your child about what is required out of public interactions. You might want to talk to her about the crowd she can expect every time she is to go to a social do. Once she is prepared about what she can expect and how she is to interact, things will get better. Also, be patient and remember that not every day is the same. One more point to remember is not to force your child to interact or to get angry with them if they don’t. A lot of introverts have been very famous personalities, who have contributed to the larger good of the world in their unique way. Also, you might find solace in the fact that most introverts have higher IQs than extrovert children because they can focus better.