Yeah that does help :)
I think it's just going to take a long time for her to truly settle down and relax about more than one horse being in the same area.
In my eyes, your daughter did not know that could happen so she was overly trusting in the situation, kind of like Snow white and the evil queen posing as the old lady apple seller. Now that she knows horses can react violently in a defensive manner, and she has been made aware of that from an unsafe perspective, she will be a lot more careful.
It's like a horse that experiences something bad (maybe the water in the hose is too hot and scalds them, so now they don't like baths.) That horse will then anticipate the hose hurting them, so they'll get anxious, try to escape, etc. Your daughter is going through the same thing. She truly believes two horses or more = the horses are going to end up in a scuffle and she's likely to get hurt. So she's going to be anxious and try to avoid this situation at all costs.
ONLY time reinforced with good experiences will help her to build her confidence. But also her understanding the warning signs of a horse will help her too so she can fully take responsibility of her own well being. Are you following so far?
If she feels nervous and unsafe, she can remove herself in a safe manner.
Same with a horse that feels threatened, we teach them in spook in place instead of running around with their limbs chopped off even when they've escaped 'the crisis.'
I hope that helps you and I appreciate you taking the time to write that all out on your phone as I know how frustrating that can be!
"Strength is the ability to use a muscle without tension"