Almost 2 years ago I rescued a Jack Russell Terrier female. Her mean owner threw her out in the street to fend for herself. When I brought her home she would not accept the other dogs I had. She would sit in the middle of a dry plastic kiddie swimming pool on the enclosed patio and just growl, show her teeth, snap out towards them never bit one or got in a fight with anybody. Behavior in about 4 months: I totally ignored it eventually one day she decided just to be friendly and she started playing and playing with toys with the other dogs getting along just great until 3 weeks ago! she was on my lap and my daughter. (22) reached over to touch her and she started growling and then snapped at her. Now she does not play with the other dogs she does not snap at them but she growls when they walk past her. she constantly has her fur bristled down her spine, that never changes. The crate she sleeps in at night and when I'm at home is on top of another crate so she usually jumps in. First thing in the morning I open her crate and she jumps out and happily runs outside. When she comes in she's anxious to get back into her crate so she can have her food. Sometimes I have to lift her up to get her into her crate and then she's growling the whole entire time. For the last 4 days she has not finished her food. Today she did not eat any at all. Twice my daughter had to pick her up and placed her in her crate gently, the entire time she growled at her, when she released the dog in the crate the dog spun around growling and snapped at her.
It is a full three weeks of the same behavior every single day. Can someone tell me what the cause might be? What might change this behavior?