It sounds like she may have a bit of fear aggression and if she is going after dogs over food she may also have possession aggression.
Fear aggression. Dogs with fear aggression only take to one person and do not trust others , even if the dog has been around them for life. They see things humans do as threats to them. Eye contact, Talking to, reaching out toward or walking toward. If they feel trapped they will act on instinct and may bite. Other animals that get in their space they may go after also.
Fear aggression needs to be treated with care to prevent bites. It is important for people to teach and use commands with a fear aggressive dog so the dog knows what you are going to do as you near it. For instance, if a dog is laying on the couch and you walk up to it to take if off the couch, the dog will bite because it does not know why you are touching it. So you would teach the dog the difference between jumping up on something and jumping off of something. This way you would tell the dog to move off of the couch before you sit. The dog gets off, it knows what you want and it goes somewhere else. Fear aggressive dogs need to be ignored by those it does not trust ,, especially if there are no commands in place. Doing any of the challenges can result in a bite. Positive obedience training such as clicker training should be kept up with through the life of the dog. Behavior adjustment training can also help.
Behavior Adjustment Training
Possessive aggression. Dogs with this will take ownership of items and will growls or snap if someone tries to take them away or they get too close to the possession . They can be possessive over items, food, people, and space.
Possession aggression is pretty much self explanatory where as the dog will not relinquish what it feels possessive of. In this case the dog should be trained daily and put on the nothing in life is free program. All things the dog may feel possessive of should be put away. The dog should be taught to go to a bed or crate in the corner if the room and stay there when company comes, especially children as children do not understand a dogs body language. Training a possessive aggressive dog to give up an item is also a good idea.
Nothing in life is free program