Take this FWIW, unsolicited Internet forum advice. My lovely always reasonable show hunter TB mare got this way at a barn I moved her to for college years ago. She was a super broke gentle babysitter type show horse who had been everywhere never with an issue. She completely lost it getting attached to a younger mare she was turned out with about a month after arriving. I’m a decent riding amateur but no way I had the skills to sort it out. Or desire frankly. Barn really couldn’t accomodate changing the turn out and she was getting dangerous to ride and handle. I put her on Regumate on rec from my vet. Fixed everything literally overnight. At the end of the year I brought her home. Stopped the Regumate and rode, showed her no issues for many years. Ultimately retired her at home until her passing without any issues. She also had three fillies for me. Great Mom. No issues to wean them.
I’ll stop. Enough info. She was my heart horse who lost her marbles. Regumate fixed it. Stopped it. Horse stayed her perfect self.
Good luck!
