Grumpy mare attacking other mare :(

[Rosehip]

My big Fell, Melly, has had problems since last sept with bone spavin, currently she is on Equine America high strength bute free, and also having a danilon every 2 (ish) days and is still showing lameness - this week it is her off hind, but it comes and goes in both even though we have had all the treatment inc the IV Tildren. She is now retired to grass as she doesnt 'do' light hacking...its more bolting and scaring the bejeasus out of me!

The problem is, that when her hocks are feeling sore, or she is cold, she attacks my in foal mare, biting usually, but tonight threw both barrels at her too. It only seems to be when I am around, as both my OH and Dad have been and poo picked/mended fences etc etc and Mels is fine with Seren then...
Im wondering if this is purely when her hocks are flaring or if its jealousy too??

Any advice much appreciated!

 

[Chestnut mare]

My mare is like that so I know what u mean! It is around feed time I notice it she starts to become very dominant and aggressive she will chase the other mare off ears back and will also turn on her n run backwards kicking at the mare with both hind legs! She never marks the other mare in any way just a moody mare!! I found she is worse on winter and they seem to fight over feed/ hay! The rest of the time they are joined at the hip grazing side by side and grooming each other! I'm not sure what the answer I kno someone who found top spec calmer a help! Have they always been out together? My Mare was always dominated at other yards but has been out with this mare for a year and is top dog!!