It is the end of term, meltdowns in my experience are completely normal. They are over tired, over stretched and exhausted.
This is no reflection on you and your parenting. As she gets older she is likely to say one or two other hurtful things, and you really must learn not to take it personally.
She is overwhelmed by everything or nothing. Consider giving her the day off if she still has a few weeks to go before finishing school.
Take time to talk to her when she is not so tired, and ask her how things are going and if there is anything upsetting her.
When you have a moment, knock on the door of your neighbour and thank her for caring about you all, and explain dd is over tired, so apologies for the noise.
We don't live attached to anyone but god knows what they would make of our nightly dramas at the end of term if they did. I have two dds, and I am well used to this.
Give her a week into the school holidays and dd will be back to her old self I am sure!