Orphaned horse, (now 5 yr. old Mare), afraid of other Horses

Question
Dear Sunny -
I hope you can help me with a horse mystery.     
I've raised my mare since she was orphaned and only 3 days old.  She's now a lovely 5 year old Palomino Mare.  She's very smart and a wonderful horse.  I taught her all ground work, broke her myself, and have been advancing her since.  She is a loyal mount, and will do anything I ask of her.  We have a very good penmanship.  I've ridden her for the past two years.  I will never compete with this mare due to her heart murmur, and because I'm now 57 - but we're active trail riders together.   

The mystery that continues to plaque me however is the fear, and territorial behavior my mare displays to other horses when we're on rides.  My horse pins her ears back, will bolt or jig - whenever any other horse comes anywhere near us.  She acts afraid of other horses that she doesn't know.  The horses that are passing us, or walking along beside us, or that come up from behind us on rides are not running, or threatening in any way.  Yet my horse still acts fearful to often, and not always consistent on her behavior.  I've been told to swack her on the neck with a crop every time she jigs, or acts negative.  But I'm not sure if that's the right thing to do to cure her unacceptable behavior.   
My horse does not live alone on our ranch.  We own 5 other horses.  They all pasture together on 42 acres with plenty of food, water, etc.  We feed every evening in individual locations, so there is no conflict or competition for food, and they are well cared for.  Thus her home life is stress free and happy.  Yes, there is a "pecking order" here, and this mare is low on that totem-pole, (so to speak), but only from a social standpoint displayed through seniority in age with our other horses.   

So, when we go on trail rides, and another horse comes along beside us, near us, or behind us, (non-threatening, even at a slow walk), my horse will bolt, jig in fear, or pin her ears back and has even tried to bite a horse.  She's kicked another horse once also.  She acts territorial, as though she's trying to protect Me?!
 
Have you ever heard of such behavior and is it related to her having been an orphan?  Will this socialization problem ever be outgrown, or a life long condition?  
My Mare is what I call an "ANTI-HORSE HORSE".  
It makes the trail rides not as enjoyable and sometimes very difficult.  
I had hoped that more and more experience would help, but it hasn't.  I've taken my mare to 2 different horse clinics, an equine chiropractor, my Vet for x-rays to make sure she's OK, a second opinion Vet who said, "many orphaned horse have a psychosis", and I've even been to a pet communicator - no help to date.  

Any advice or suggestions would be greatly appreciated!!!
Ms. Lynn  
Lynn

Answer
Hello and thank you for your question. I have heard of orphan foals growing up to have different attitudes then most other horses. I really don't think that you will cure your horse all together from this. I have a gelding (not an orphan) who is very fearful of horses coming up behind him, his eyes bug out, he gets faster, and wants to get away from them and its horrible because hes my good show horse. I have done a few things to help him for this. First I started to pony my other horses off of him, he knows the other horses we have and will not kick at them but he gets a little tight so I just keep leading another horse behind him every day a new one for a week or two. You can let a good friend with a good horse pony her too she will learn to be with an other horse and follow. It did help, next was a good suggestion I got from a World Champion Western Pleasure trainer that I know well. He took my horse for 2 weeks for a tune up this spring and I told him of this problem. He Tied my horse up on the outside of the arena and rode all kinds of horses by him. He said at first he about jumped out of his skin but after a few days he just fell asleep while the others whizzed by.  I would suggest also to have a good friend with a good horse to ride with you, first infront,then beside, then behind. Let your horse follow and get close to your buddy, when she acts up have your buddy stop and you need to make your mare work hard trotting circles and changing directions. After a few let her walk behind the horse again if she does it again, put her to work and longer every time. When she can follow happily, ask the buddy to join beside you, if your mare goes to kick/bite/bolt etc, ask her to go back to work and make it hard work. She will realize that if shes good she can enjoy herself, when shes bad she has to work. Then try having your friend move behind, walk and if your horse gets nervous ask your buddy to stop and make her work again. This isn't something that is going to be cured over night. It will take time and practice. I hope these suggestions help. Best of luck!