My Jack Russell, growls and shows her teeth

by Vikki
(United Kingdom)

I have 2 Jack Russells, my eldest marlee is 20months old and is extremely possessive over toys, shoes, her cage, everything at the moment. She has even pinned my mum to the sofa or stopped us from getting out of a room due to the snarling, baring of teeth and the fact that she would bite.

We have no idea what to do, she goes to dog training and is a very nervous dog generally. She is scared of other dogs and people and nervous of loud sounds.
She is nice with the puppy but we are scared she may turn.
Can you please offer advice as we are not sure what more we can do for her.
Thanks