How should my mom train her dog to not fight?

I'm living with my mother while going to college, she has a female german shepperd and a few months back she got an female English Mastiff. The mastiff is 10 months now and she bought the mastiff from a breeder. The mastiff is fighting with the other dog over anything and everything we have to feed them separate but we have an automatic water feeder outside and the mastiff will fight over that as well. The mastiff is in the process of being trained for dog shows and the way she's acting we don't know what to do. When we first got the mastiff she would growl at everyone even the kids when she ate, she doesn't do it anymore but she still fights with the other dog. She growls, barks and ends up attacking the other dog. We try to keep them separate but we want them to get along. How can we train my mother's mastiff from being so violent? What should we do to keep the dogs from fighting? We love them both so much we don't want to get rid of them. Any advice greatly appreciated,