the law is about technicalities so technically she's correct. However driving in such a manner is horrible. If she fights it, she will most likely get off, unfortunately.
I've found the same situation here in Sydney. Some of the second hand stores are so expensive I won't even bother to look there anymore. I may as well buy from Kmart.
Do whatever you have to do to get through. He could have washed the dishes properly in the first place. Go mum.
I'm pretty sure he won't die from this lesson. Do whatever works. Go mum.