There is nothing wrong with what you said, it is the truth. Neighbours COULD get concerned and report to social services.
I think some kids have a very strong sense of right and wrong or unfairness. And something that might seem very trivial to an adult may be huge in a child's head. I do think that sometimes they just want to have their feelings acknowledged, rather than dismissed as silly or trivial. Or they get very frustrated at a parent just saying "no" or "because I said so" to a request when there is no good reason for it.
I have known some parents make a habit of saying an immediate and to the point "no" to a child just because they can't be bothered with a lengthier discussion about it, or because they think they are too busy to do the very quick and simple thing that their child asked for, or simply because they as an adult didn't think the thing was worth doing. It becomes a default answer, and no wonder the child gets frustrated, they have no choice in anything.
I'm not saying that is you, OP. But with my kids when they were little I've always tried to get in their head and understand where they were coming from. I am not a soft parent and have very strict boundaries (but I've never been scared to change my mind about allowing something, on reflection, as long as it's with a good explanation to the child about why I've changed my mind, so they know it's not just you "giving in" to their demands.)
So, for example, OP, you say your DD has meltdowns at trivial things. Could you try seeing them instead as being very important to her rather than see it from an adult point of view? Might that change how you react to her requests etc? So if something she's building goes a bit wrong, rather than see it from an adult point of view and think "oh fgs, what does it matter, she can easily do another one in two mins, this is a total overreaction and I haven't got time to help her because I'm trying to cook dinner", try and get in her head and see how it might make her feel like a failure, defeated, frustrated etc.
I don't know, maybe it might not help. Maybe you've tried it. But sometimes just trying to put yourself in their shoes,and just acknowledging their frustration, vocalising it to them, might help.
eg. "Ah, what a nuisance that it fell down, that can sometimes be VERY upsetting, can't it, when that happens? It was a lovely thing that you made, you're right, I was admiring it while I was peeling the potatoes, but I bet we can build one together that's just as good if not even better, would you like me to help you, or shall I just watch you?"
Some kids are naturally resilient and just pick themselves up and get on with frustrations. For other sensitive or SEN children it's a major thing and just having an adult acknowledge their feelings really helps.
I hope that doesn't come across as patronising....and you might be already doing all these things anyway....