I will have to think about that idea.Could you ask your helper to put the concoction in the brooder pen with the door open, so Minnie could access it? My thinking is that she might be more likely to go in there to eat it since she is used to that and the others aren't.
I don't have a good picture of your set-up in my head, but am just throwing out ideas.
I think she prefers the rough-and-tumble of being with the others so I am not convinced she would jump up to the brooder voluntarily. Diana however would go in there if she thought there was food.