Forensic officers remain at the scene as investigations continue.
One shop keeper said Amal came in his store regularly with her daughter.
He said he believed she had recently helped her husband move from Somalia via Italy so they could be together.
"She had helped him come over and he only got here recently, so I don't know him," he said.
"But she was a lovely young girl. She was quiet and always polite.
"We are just all shocked that this has happened.
"She has got other relatives in Bristol as well. Her family will just be devastated. It is such a sad situation."
Another neighbour added: "There were police and ambulances everywhere on Sunday.
"No one really knows what happened, but a lot of people have said she was pregnant and was stabbed.
"Forensic teams have been coming in and there have been police everywhere. I think she lived with some of her family, including her cousins.
"She was a young Somali girl, a pretty girl. It is just devastating that this kind of thing can happen to someone so young.
"It's such a waste of life."
A spokesman for the police said: "We can confirm that the woman who died on Sunday in the incident at a in Morley Street, Barton Hill was Amal Abdi, aged 21.
"Amal, who is Somalian, was four months pregnant and the post mortem has confirmed that she died from stab wounds.
"A 21-year-old man who was arrested on suspicion of her murder remains in police custody. A further warrant of detention has been obtained, enabling officers to continue questioning him.
"Specially trained officers are supporting the woman's family and the local neighbourhood policing team are patrolling the area, providing reassurance and receiving information from members of the local community."
A resident who lives in sheltered opposite said: "I heard from her cousin that she got stabbed. All I've been told is that the girl got stabbed.
"It was swarming with police and they've still got one over there.
"Yesterday they had one of the forensic vans over there too.
"There were half a dozen police cars, two ambulances and paramedics everywhere. We couldn't get in or out of our building."