Separation Anxiety and New Pasture mate unhappiness- Please help!!

Hi there everyone I’m new here but I really hope someone will be able to help me!

I have a 22 yr old Haflinger mare who I’ve owned since she was 12 (previously an Amish pony) who this past July lost her paddock mate when she (the paddock mate) was sold to a farm in NJ. They were very close even though they had only been out together since October 2014. Understandably, she was quite upset when the pony left but adapted to being alone within a week. She was then alone in her paddock (with other horses in neighboring paddocks) for a good three weeks before a new pony moved in that was meant to be her new buddy. The initial meeting went fine and the first night I left the barn they seemed fine but then I got a call from barn owner that night saying that Mercedes (my haffy) was pacing and spazzing out so she separated them. The other pony then went out in the next paddock over and it took Mercedes two days to settle down again by herself but then barn owner decided to try them again together last night and said they seemed fine. This evening however I went out to get her for a ride and she came galloping over to me and then practically dragged me into the barn (she usually has perfect manners) and then when riding in the outdoor refused to walk past the part that is next to her paddock where the other pony was and it took me teeny minutes to get her to pass. When I put her back out she trotted around for a few minutes and then was going back and forth from grazing to pacing when I left.

Any suggestions on what to try??

Barn owner suggested bugs because she had hives and was itchy. Talked to vet who said could put her on dexa but did not want to because of laminitis risk. I believe the hives are from anxiety but do not know for sure…

Thank you for your help!

Sounds like it could be bugs and she is so uncomfortable that she wants out of there. I saw a horse just run back & forth to try and get away from eating mosquitoes . Is she izzy? Oatmeal baths might help.