A teenage boy was arrested on suspicion of murder outside nearby Worle train station at 6.19pm. He is being held in police custody.
Neighbours said that Aria celebrated her ninth birthday two weeks ago with a K-pop themed party.
One family friend said she loved dressing up, having her hair styled and wearing make-up.
Neighbour Tamara Taylor, 40, said: “Aria was a lovely little girl, sassy for her age, she loved dressing up and doing what little girls do.
“She and my daughter were best friends; they were always playing together and would be in each other’s houses every night.
“I’m dreading telling her when she comes home from school later.
“How do you tell an 8-year-old girl that her best friend has been murdered?”
The two schoolgirls had even set up a small car cleaning business to help pay for their make-up and clothes.
Aria and her friend were looking forward to Christmas and had been planning their present list together in the days before the stabbing.
Aria, a pupil at Beckett Primary School, lived in a three-bedroomed housing association property with her mum, Victoria Hull, also known as Tor, who worked in a local salon.
In a message on Facebook, the salon wrote: “Tor has had some devastating news and is mourning the loss of her daughter. The salon will be closed until further notice.
“We are all heartbroken and ask you to be respectful at this time.”
A large police cordon was extended on Tuesday as police and forensic officers investigated the murder.
One neighbour said: “It’s terrible at any time of year, but at Christmas, it’s too dreadful to think about”.
Another resident, Glynis Field, said: “I’ve never seen so many police cars in all my life, and ambulances, armed police.
“Forty-nine years we’ve lived here, and to think that’s right on our doorstep ... it’s awful, terrible, absolutely terrible.”
On Tuesday evening, floral tributes were laid at the edge of the police cordon.
A young girl, who was visibly emotional, laid a bouquet at the scene with a note that said: “Aria, thank you for playing with me”.
‘Utterly dreadful news’
Superintendent Jen Appleford of Avon and Somerset Police said the whole of Weston-super-Mare would be “distraught and shocked at this utterly dreadful news”.
She told a press conference close to the murder scene: “The ambulance service called us to a house in Line Close shortly before 6.10pm. Tragically, a young girl was pronounced deceased a short while later.
“A teenage boy has been arrested on suspicion of murder and is currently in police custody.
“The girl’s family were informed last night of what had happened and our heartfelt condolences go out to them.
“It is impossible for us to adequately put into words the pain and anguish they are feeling right now.”
Appleford said the family would get the support of specially trained officers.
She added: “We do not believe there is any wider risk to the public but extra patrols are planned in the area.
“Our major crime investigation team is leading the murder inquiry. We will continue to provide updates in due course.”
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