Has her aggression been present all her life? Or is this something that just came up? I have heard a lot of ideas that "aggression" with age can be due to health issues. Has she been to a vet for an exam within the last year? One of my chihuahuas and my lab/border collie mix are food aggressive... we just keep their food up unless they are eating and when they eat they are crated separate from the others.I have a JRT. She loves people but I have 2 other dogs and 2 cats. It was a miracle that we finally got her to accept the cats. She is dog aggressive. She gets near the dog food and guards it from the other dogs growling at them and even the cats if they come near. She even growls at us sometimes but not sure what that's all about. She has snapped at my wife a week or so ago.
We have a small toy rat terrier and she growls at her sometimes too. The JRT is 12 years old and has been with me all her life. My wife hates her and I really can't blame her. I'de like to find out a solution to all of this. If we can't, we will have to do something about her. I think she would do well in a home without other pets but I hate to get rid of her if there is something I can do to change her. Any ideas anyone? anyone? Bueller?
Also is your wife pregnant by chance? My sister had a white schnauzer for years and when she got pregnant he turned on her for some reason as well as her husband. I think a professional trainer can really help you as Crio suggested. If this is how the dog has been and it is not recent, then keeping her separate may be best for her. Re-homing a pet with these issues sometimes is only harder on the dog. I do not think it sounds serious enough to consider that GL and keep us posted.