to not want my DD to have sweetner?

[Tw1nkle]

My MIL has been looking after my DD today, and she knows that I don't have any sweetner at all (it makes me feel ill), and she also knows that i don't want my DD having any (there is no need, she is only 2.4).
So when i got back she went into the kitchen and came back with a half drank bottle of flavoured water, and asked it if was ok for her (DD) to be drinking it (after she had already clearly drank half the bottle!!!).
I kept calm and told her i'd prefer it if she tipped that drink down the plug and refilled the bottle with plain water - which she then did.
But AIBU to assume that she wouldn't/shouldn't give DD sweetner in the first place?!!?

Hi,
I did provide all the food she would need for the day, and a drink of diluted Apple Juice. My MIL knows that my DD drinks plain water all the time.
Yes, she may not have realised that the water contained sweetner, but she would have given her more, after finding out, except I was there by that point!

I know of websites that detail the dangers of sweeteners, but not specifically for Children - does anyone know of any? I can then print it out and show MIL (In a nice way of course!!!).