Raneem Oudeh, 22, made multiple calls to emergency services on the night she was killed alongside her mother Khaola Saleem, 49.
Police struggled to locate the pair until a later call where the “situation escalated” and officers were dispatched, arriving “within minutes”.
They were found with fatal stab wounds on Northdown Road in Solihull and treated by paramedics, but pronounced dead at the scene.
Detectives have now stepped up a manhunt to find Janbaz Tarin, Ms Oudeh’s former partner.
They announced on Tuesday that a suspected murder weapon had been recovered.
Computers, mobile phones and a van have also been seized after searching several addresses to track down the 21-year-old Afghan national.
Tarin remains at large and police are appealing for information that could lead to finding him.
Detective Inspector Caroline Corfield, who is leading the investigation, said police had received many calls from the public with leads.
She issued a new appeal for people to come forward with any information or sightings of Tarin.
“We have a team of detectives working around the clock to try and trace the killer and get justice for Raneem and Khaola’s family,” Det Insp Corfield said.
“The response from the public to our appeal has been positive and we are following up all credible lines of enquiry – but we need anyone with information on Tarin’s whereabouts to get in touch.”
Earlier, neighbour Sarah Hollis described victim Ms Oudeh, who had a two-year-old son, as a “lovely woman”.
“She was quiet and they argued quite a lot – near enough every day,” she told Sky News.
Ms Hollis said she could sometimes hear Ms Oudeh “shouting for help” in her “constant” rows with Tarin.
“It sounded like she was getting whipped or something. You could hear the little boy crying on the balcony.”
Anyone who sees Tarin has been asked not to approach him but to ring 999 immediately.