JRT behavoir problems

Question
I have a JRT puppy who turned a year old in May. We took her to puppy classes at PetSmart and they went well, she is a smart dog but the problem was no one else signed up for the puppy classes so she never got socialized with other dogs. There are two Chihuahuas living in the basement and as soon as my puppy got ruff with them, there owner decided to ban her from seeing the other dogs. Because she was never around any dogs, she doesn't do too well with them. Aside from other dogs, she is usually loving with people. The recent problem is that my puppy has a guarding issue. She has to eat in her kennel because she will attack the cat, or if there are dog treats or toys laying around and someone tries to go pick her up or kiss her, she'll growl aggressively and lunge at your face. She has never hurt anyone badly but she scares you so much that sometimes I am afraid to get near her. When she does growl we tell her NO and we growl back. This is because we heard this should teach her that she is not in charge, and that she cannot do that. The problem is, it doesn't seem to be working. I don't want people to be afraid of her but I don't know what to do. Is there anything that should be done differently? What else can be done, anything?    Thanks!!!

Answer
Hi Sarah,
Your dog has been in charge and the leader of your pack for over a year now! Yes, socialization with other dogs is important but not only during puppy kindergarten. She should have been socializing at a dog park or other classes continually for the past year.
She definitely has an aggression issue that seems to be escalating and has to be stopped immediately (before someone DOES get hurt).
The first thing you have to do is take back the leader position. YOU are the leader, not her. She can absolutely feel and see that you are afraid of her! I don't know if I can explain to you in this little space of what you should do, but I'll try....
Number one, get a nylon training leash - one that will tighten if you pull it - NOT a choke chain, but a LEASH that goes around the top of the dogs neck right under the chin. Next you have to take her out for a good long power walk and get rid of some of her energy and aggression. You have to control the leash and her - don't let her PULL you along. When she gets aggressive, you have to pull up on that leash and give her a firm touch that simulates a mother dog correcting her pup - you use your hand and give a firm nudge/squeeze on the back of her shoulder/neck and say the sound "psst" at the same time. I know it sounds whacky but it's so hard to describe here. What you are doing is teaching her in dog language, and redirecting her and breaking the concentration that she has on being aggressive at that moment. Mother dogs don't use words when teaching their young but the pups KNOW who is the boss right from the start.  The SECOND she shows aggression you need to do this correction and if you aren't close enough, just point and use the sound. I HIGHLY recommend you watch Cesar Milan, The Dog Whisperer on The National Geographic Channel - it's on Friday nights in Eastern Mass but I know it's on nation wide. You can also go online to his website or get a book and tapes on his method. They are amazing and work wonders - it's just so hard to describe here.  
I hate to say it but her behavior is only going to get worse if you don't stop it now. She's been running the roost for a year now! Find a dog training SCHOOL in your area and sign up for some behavior classes, Petco is not a good place to train your dog. Puppy K is OK for a start but shouldn't have been the only training.
Very very best of luck! You CAN get control back but you have to start now!