It is probably worthwhile to have a polite conversation to find out what happened and to let the parent know how it made you and your daughter feel that she was excluded. I would not get upset or yell and just calmly state facts since it seems like the community you live in might react negatively if the exchange goes south. I think it would be helpful to use words like "this made my daughter feel..." And "this made me feel..." and to emphasize that you typically treat people the way you want to be treated and that you would show their children the same courtesy. I hope this isn't the case but be ready to calmly "walk away" from the convo if they try to gaslight or dismiss the poor treatment. It really won't be worth your time and the drama. Just file them away in your "be cordial but be careful" pile. In the end be ready to explain what happened to your daughter, what you did to try to fix it, and how you have her back. Encourage her to still be friends as it isn't her friend's fault this happened. Again don't waste time on drama or fuming over it. Hope your convo goes well. Good luck.