Marina was born in Russia with congenital limb deficiencies which meant her legs and arms did not develop properly.
Her parents Jo and Gideon Pritchard first met her when physiotherapist Jo was working for a charity, The Promise, which works in Russia and neighbouring countries training carers and healthcare workers to support the development of children with disabilities.
They adopted her, and brought her home to live with them in Devon, when she was two.
As she grew up, her disability meant that she could not always do the same things as her friends, which affected her confidence.
But then Jo and Gideon, who are puppy walkers, took charge of a trainee police dog called Tag - and an unexpected friendship began to blossom, which has transformed eight-year-old Marina's life.
Mum Jo says the close bond between the two has has helped Marina improve her confidence and energy levels, while her enthusiasm for life has soared.
Marina, who lives in Exeter, now spends hours playing with the dog and goes with to all of his training sessions.
Since meeting Tag she has also become more active, enjoying running, tennis and swimming, after having custom sports prosthetic running blades made.
The blades were made especially for her after a chance meeting with the Paralympian Richard Whitehead, who arranged for Marina to go to London and have the blades fitted.
Mum Jo, a children's physiotherapist working to help other children with limb deformities, said: “Marina has had a special relationship with Tag from day one.
"Tag knows when Marina and her brother, Seth, are on their way home from school and waits at the gate to greet them.
"Marina has always loved animals, but her relationship with Tag has improved her confidence.
"She loves telling people about him and that she is helping to train him to be a police dog. She is also more aware of routines due to needing to think about when he needs a walk, feeding etc. They've become so close she even asked if she could be his main carer."
Devon and Cornwall police canine development officer Paul Glennon said that the bond between the two is unique, and that Tag shows unusual sensitivity and gentleness when interacting with the little girl.
He said: "It was clear to me straight away at our police puppy training days that Tag and Marina were very close.
"Tag is an intelligent and calm puppy and adores Marina.
"He seems to understand her disabilities and limitations and is incredibly gentle with her, which is amazing for a dog of his age.
"We have high hopes for Tag moving forward to full police dog training when he's old enough."
Marina explained why they get on so well: "Maybe it's because I play with him most of the time and he just loves it. I love puppies and I think Tag is one of the best puppies I know.
"He is my best friend. He is basically my special BFF."
One day Tag will have to leave to continue his police training, but Marina is prepared for that. She said: "I'm going to be very sad but I know he is going to be a very cool police dog and he is going to catch loads of baddies."