Las Vegas, Nevada - When little Ariana left our world forever after a serious illness, she left behind not only her grieving family, but above all her best friend – Bella the dog – who still doesn't understand that the girl will never return.

In a video that has been clicked several million times on Instagram, Ariana's mother filmed how the four-legged friend is doing now over a year after her daughter's death.

The dog and the girl, who was diagnosed with cerebral palsy and a hearing disorder, had formed a strong bond from the very beginning.

"She wasn't just Ariana's dog – she was her best friend, her soulmate," the girl's mother said in the post's caption.

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Although it was not possible for Ariana to romp around with her dog like other children, the pup never left the little one's side.

In the clip, you can see how Bella initially watched over Ariana when she was still a small baby. Later, the parents filmed the two of them cuddling and how the dog chose Ariana's lap as her favorite place.

When Ariana died, her parents, sister, and their dog Bella were on vacation.

Although the family took the animal with them to the funeral to give the four-legged friend a proper send-off, Bella still seems to be waiting for Ariana's return.

According to her owner, the twelve-year-old animal still waits in the little girl's bed every day.

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Of course, the family tries to comfort the animal as best they can, but they know that they can never replace Ariana's role in their pet's life.

As the pooch has already reached an advanced age, Bella the dog may see her best friend again someday soon.