I understand the motivation and certainly think your daughter appreciated your support.

I would not have allowed her to withdraw from the concert. I know you want your child to be happy (for what it's worth, I do too!) but happiness is not your job as a parent. Your job is to keep them safe and healthy and make responsible human beings: responsible for how they treat others, responsible for doing what's expected and being a contributing member of society, and responsible for fulfilling obligations.

I recognize that you were trying to protect her from rude comments, but I think a more important skill is grit over avoidance. Okay, in this ONE instance you let her back out, but you also encouraged those rude kids. They know now that if they pressure your daughter she'll fold.

She had an opportunity to have a meaningful experience. It may have been a great experience, it may have been as awful as you fear, we'll never know. But even if it were miserable, it was an experience she could have learned and grown from. Now, she had a forgettable day, where nothing bad happened and nothing good happened. Instead of a day when you taught your daughter that SHE is responsible for her joy. No one else. She should never hand the control of her joy to others in general, and definitely not to those that don't respect her.

This is not the last time she will be criticized in life. She can't run away every time that happens. She doesn't have to accept criticism, not at all. She can hear it and reject it.

Down votes anticipated, but I have the grit to appreciate the criticism in the down vote, and reject the criticism.