
I am so sorry the OPs daughter had a bad experience. Don't have a lot of helpful advice to give I am afraid, but while I understand how awful it must have been to see unwelcome behaviour aimed at her daughter we have to remember these are kids, and as well as they may be been taught about fairness to all, no discrimination etc., a lot of this will simply fly out of the window when it comes to a sort of "spoiling my chance of qualifying" type of thing, just because they ARE KIDS. A lot of the JH kids are extremely focussed on what they are doing, I would hope that in an everyday enviroment they would find their behaviour appalling, but being kids they don't tend to think around a situation too much. This is not an excuse but a possible explanation. I have had to point out to my JHandling nephew that he is shooting filthy looks at someone outside of the ring who has deposited chairs, show stuff etc with a crash ringside and broken his dogs concentration - he was completely unaware of his facial expression or having done so.
We have a young lady in pugs who handles beautifully in the breed ring from her chair, I have never see her doing JH however. The pugs sometimes glance at her chair the first time they meet it, but I have never seen one scared of it - after all they see so many strange wheelled contraptions at shows with trolleys, show cruisers, push chairs and even the golf buggy's used by committees.
I do wonder about the logistics of JH from a chair, not just the patterns as mentioned above, but also shadowing - I would think this could be very difficult? IT might be an idea to start of with some YKC stakes classes, that way she could get to know the other kids in a straight forward showing based class and polish up her basic skills, then imove onto handling classes in a little while?