I think my horse has gone bonkers

3 days in a row, Maggie has attacked someone. Twice she has gone after the barn manager and today she went after her former owner (who is now boarding her horses at the same place we are). Yesterday, D, the barn owner/manager called me all huffing and puffing and told me that Maggie had gone after her when she was carrying hay to the mini horses. Maggie bit D's ear and then turned and kicked her twice. Today Maggie went after her former owner (who owns the minis) and knocked her down.

We're all just flabbergasted because she has never acted this way before. My kids won't be getting back on her for a while, until we can do some ground work with her and figure out what the hell is up with her.