If you try to see it as a developmental stage rather than a behavioural problem, does that help?
At this age, they push, hit, pull hair, bite (thank your stars she doesn't do that one!!), pinch, kick and it's nearly all to do with their lack of verbal communication. As their verbal ability increases, they learn better ways of attracting attention and getting their views across.
That's not to say you ignore it. You deal with it in whatever way seems best to you.
My own is to say firmly, in as deep a voice as I can manage: "No! Hitting hurts!" before checking that the other child is ok.
If it's a very young child, I'll then soften and lighten my tone as I say and model "Gently!" or "Nicely!"
As soon as they're old enough, I insist on a "Sorry!" being said, or they can cuddle for sorry or sign it.
We then have a Big Hug group cuddle together.
If the other child is hurt, he or she gets most attention and cuddles before the group cuddle.
I shouldn't think the other childminder meant to sound so judgemental. I've offered advice at groups before and I'd be mortified to think I'd upset anyone.
A bad childminder, by the way, wouldn't even notice any of the incidents until brought to her attention, and would then shrug and carry on chatting when told. Thank heaven, they are a tiny minority.