Help! Horse aggressive during feeding time!?

My 21 year old Quarter Paint mare has issues with feeding time. She is crazy about grain and we thought about taking her off of it but shes old and its senior grain that helps her with other needs. We have tried holding her, but she drags us around, even with 4 people. we tried shutting the stall door but she kicks it and chips the wood. If someone doesnt get her grain, she goes after them. She is also constantly wanting to go to check for grain in her stall, even while riding. We have to duck when im riding her and she goes barreling into her stall out of control. If we are in the stall trying to feed her she comes in and we scream BACK!!! OUT!! but she turns her butt to us as if shes going to kick us. we have only owned her for a couple months but her previous owners left some of her bad habits alone. This is a dangerous habit and i need help!