What worked with my mare was to make her work HARD every time she so much as made a nasty little mare face. She really was evil with other horses, and was starting to try to pull an attitude with me as well - threatening to buck, bunny hopping, and bad little attitude in general. I was being generous in thinking maybe it was a pain issue, rode through everything, and tried my hardest to figure out what her issue was.
Finally her breeder came out, and said "Well she's just like her mother, isn't she?!". If she tried any of her mare-ish stuff, he backed her up, turned her, circled, flexed her next, basically did anything to keep her very very focused on the rider. I'm very happy to say that we no longer have to put a red ribbon on her tail, so long as I'm very aware of her attitudes towards other horses. She's allowed to not like another horse, but she is NOT allowed to act upon it - when she is under saddle, she is working, and she better pay attention to me!