Well, I think you need some guidance from a good dog trainer. Maybe a couple sessions would offer help that you can use yourself to retrain her. You just need someone with good experience as this isn't your usual "sit/stay" training.

Try relocating her food. Maybe put her food down at eating time only, limit open feeding.

Sorry you are having so much trouble. I hope someone else here can come along and offer some suggestions.

You didn’t say how long you’ve had your rescue doggie. It would also be helpful to know if this is your first dog or if you’re experienced with dogs and if you are familiar with the breed traits of Jack Russell terriers. I strongly believe the answers to my questions are needed for anyone to offer any useful advice. @socks is spot on about relocating her food bowls & limiting open feeding! Keep water bowl down always but take up food after meals. If your pup had to worry about where its next meal was coming from there are certain to be food issues. Shock collars for this dog would be, IMO, inhumane. I assume that you are walking your dog on leash only for your safety as well as the dog. I’d recommend a Gentle Leader type harness which a trainer would tell you about. Gentle on the dog & gives person the ability to control without choking dog with a collar while pulling on leash. A trainer who specializes in gentle & reward based training is absolutely necessary!

I have had her for 3 and a half years now. I had family dogs growing up and my sister's dog was a huge part of my life too. I do have experience with dogs but (socks) I definitely think that you are right and (kw). She's never been trained before but she's also had a lot of abuse before so it's hard to tell what's going on.

Alan, it’s a good time to be looking for training to start right away! Spring is coming & things are opening back up for us all. Maybe you can get some recommendations from your vet and a small specialty pet supply store. Your pup needs more special & specific behavior therapy & training than the big pet supply stores can provide in their classes. Even though you’ve had your pup for over 3 years, she learned her behaviors to survive & hasn’t forgotten them. Jack Russel terrier’s - any terriers for that matter - are very well known for their spunk & stubbornness! They are very smart dogs. Have you picked up her food dish so it’s not out when guests come to your home? I wondered if she has relaxed a bit since she doesn’t have to worry about guarding her food all day! Sounds like shes‘s lucky to have found you to take care of her.

Thanks for the advice sorry responded late will keep you posted.