We put Justus in the herd first (after taking Jessie out) and she promptly began kicking the crap out of every other horse in there. :roll: She did the introductions, sniffed some noses, seemed to be getting along, and then went "AHA! I AM FASTER THEN YOU!" and just letting fly with her back feet. They learned pretty quick to just avoid her. So we let them sort and settle for about 15-20 minutes, maybe half an hour? They all started settling and eating, so we finally turned Jessie out.
I honestly do not believe the arena would have gone ANY different if we hadn't led them back to each other - I know we did some things wrong, but I think this would have been a LOT uglier if they hadn't gotten that out of their systems in the arena. Jessie just made a beeline for Justus, and Justus only backed down because Jessie nailed her in the hock (we checked her, she's ok, a bit swollen but not lame). However, they seemed to sort it out quite fast. As long as Justus keeps her distance, Jessie is content to keep "her" herd with her and leave Justus and Jynx alone. We stayed for about an hour, and there wasn't another bout of squealing after the last video. Justus keeps perking her ears and following Jessie, pretty sure she's happy to "give in" and try to find her place in the herd - she's a smart pony!
Some of the vids:
I think they'll be fine - Justus knows to stay away, and I wouldn't be surprised if they actually became friends at one point. Justus seems pretty intent on getting herself into the herd!