My childcare centre has FedUp available for borrowing so I'll look into that when I drop the boys off tomorrow. I've stripped their diets before and did notice a bit of improvement so it might be worth looking into it further. Fingers crossed I can learn how to cook well enough as not to need many tins/premade sauces. School snacks could be a huge battle for me to make things.
MIL is also going to contact a friend of hers who deals with children with difficult behaviours to get some pointers for us on how to defuse her before it gets too bad and also pointers on what to do when she is having her melt downs.
DH & I tried to talk to her tonight but she can't explain/articulate why she does it and what we could do to help her calm down. Not much help sadly.
Thank you all so much for your support and suggestions.
This parenting gig is so damn difficult.