Broken zipper on first wear

Hello, I'm writing because I'm really quite disappointed. My daughter wore her new dress to a birthday party on the weekend — it was the first time she'd put it on — and the zipper completely broke. Right there at the party, in front of all her friends. She was so embarrassed and upset, I actually had to take her home to get changed. It really ruined the afternoon for her. I know kids clothing cops a beating but this was literally the first wear. The dress wasn't cheap either so I really expected better quality to be honest. I still have all the tags and everything, it's clearly a problem with how the zip was put in. I just want to know what can be done about this. I can send photos if that helps. Samantha Khoury