Professor Dame Elizabeth Anionwu has paid tribute to Simonne Kerr who was killed in Battersea on Wednesday.
Kerr, 31, was a nurse and worked with Dame Elizabeth as part of the Sickle Cell Society.
The two became friends after Kerr's son, Kavele, died aged six of the blood disorder. Since then Kerr became heavily involved in the charity and was part of the NHS B Positive Choir, which appeared on this year's Britain's Got Talent.
Dame Eilzabeth told ITV London: "She was a wonderful character, beautiful character."
Kerr and Dame Elizabeth met in Manchester recently during a celebration for the 70th anniversary of the NHS, at which Kerr was "full of life".
"The world needs to know about Simonne; somebody who had such tragedies and stresses in her own life could still so much to others.
"And yet, Simonne had this tragedy but the thing about Simonne was that she was so positive, she really was."
Desmond Sylva, 40, has been charged with the murder of Kerr in her home in Battersea, south-west London.