5 year old throwing fits

[kindertime]

I think you've covered all the bases. Mom is bribing her with treats so why on earth would she ever stop? Whining is manipulation and bribing is negotiating. So as long as mom is negotiating with her daughter to stop manipulating her, it will continue.

It is annoying, I know. I got so fed up one morning with a parent for the same thing. 4yo dcb was whining and mom was bribing. It went on and on for 15 minutes. I do daycare in the main part of my house, its a bungalow and not very big. We could not get on with our day while this was going on at the front door. I got so fed up I said to her "are you done?" It was rude, I know but come on! She finally put an end to it and left. Peace returned.

Ultimately, she isn't your child so you can only do what you are doing. Ignoring it.