[user104658]

Violence is never acceptable and smashing up their stuff is violence. Is it as bad as direct physical violence? No, of course not, but that doesn't make it OK. I used to be firmly of the opinion that people hitting / trashing "things" wasn't a big problem so long as they never actually hurt a person; but it isn't. It's aggressive, it's intimidating, and it's utterly wrong-headed. It's wrong even with another adult, let alone child, who is totally at the mercy of adults.

Yes it's "her money and her decision" - if her decision is that they aren't to have them any more then fine. Take them away permanently. Sell them. Donate them to a school, maybe? Absolutely no need to "make a point" by losing the rag and smashing them up. A pretty clear sign to all involved (including the kids) that she had lost control of the situation and of herself, and yeah, that IS "bad parenting".

And yes all parents make errors. An incident of bad parenting doesn't make someone a bad parent. But you can look back on your less-than-perfect moments and say "OK... I didn't handle that very well" and try to learn something from it, instead of becoming indignant and holding it up as a badge of honour as if there's nothing to regret.