>>40574431She was pre-occupied with her job, just like her assistants, so they let the living area go, Brock loves house work, what Prof. Ivy did was far beyond the usual rejection as seen countless times in the anime, it's something only the parents watching would/may get, children just see a sad Brock.
I'm sure there are many theories on this, but mine is:
She sent Brock away and rejected him at the same time, she yeeted him back to Kanto, that's why he is depressed over it, rejection with a side order of yeeted off!
I think early Pokemon was meant to not hide anything from children, emotionally speaking anyway with two counts of guns, one of which was banned.
She may have yeeted him off for his own good, to help him grow, to find his path, she may have even been the one to suggest being a Pokemon doctor, but he needed to grow, meet new Pokemon and learn.
Where he saw an act of horrible intent, it may have not been, she did it for his own good.
