Police had previous contact with a 29-year-old knife attack victim and the man suspected of killing her, it has emerged.
Rwandan national Linah Keza was found dead by paramedics called to her home in Leyton, east London, in the early hours of Wednesday.
A 38-year-old man arrested in connection with the stabbing is being questioned over the death at a north London police station.
A spokesman for the Metropolitan Police said it had "voluntarily referred matters" to the Independent Police Complaints Commission, adding that "it would be inappropriate to comment further".
Meanwhile, Ms Keza's brother, Jack Hodari, described his sister as "the best person you could ever meet".
He told Sky News: "When we were growing up, she was very smart, very helpful, very loving - just like any other African child.
"Even though she was in the UK and I was in Africa, we would talk every day. We spoke on Facebook, we used WhatsApp, we would call - we were always in touch.
"She would tell me her worries, her excitement - she would always open up to me as her big brother.
"It really pains me that I was not there for her at the time she was killed.
"That I could lose someone so dear to me is like a bad dream."
Ms Keza, who leaves behind a three-year-old daughter, was on the books at the agency AMC, which described the former Miss Africa contestant as a "very compassionate, amazing and a professional girl".
"Today is a very sad day for AMC as we have had the sad news that one of our models, Linah Keza, has passed away in tragic circumstances," the agency said in a statement.
"Anybody that has met and worked with her via the agency will miss her greatly."
There was a further outpouring of tributes to Ms Keza on a dedicated Facebook page
Anita Karissa wrote: "RIP pretty lady, may God bless n strengthen ur lito gal thru ths n e rest of her precious life."
Another, Priscy Jay, said: "R.I.p lenah. may God strength, most especially the little one."
And Brens Willie Wambedde added: "Rest in Eternal Peace."