Sour Grapes

I was in the kitchen making dinner last night and listening to my daughter play with my son. They were both giggling. Then, I heard coughing. I stepped into the living room to find my daughter trying to feed her brother some grapes.
Luckily, he spit it out. I've told my daughter several times that her brother can only have milk and baby food. She says she was just trying to share. It's a tough situation. I thank her for wanting to share with her brother, but insist that she ask me first. In the mean time, I'll have to pay even more attention to my daughter during snack time.