The police, who are retaining “an open mind to any motive”, said a 29-year-old man was arrested on suspicion of murder on Saturday and remains in police custody, whilst a 37-year-old man who was also arrested on the same day has been released under investigation.
Ms Fauvelle’s brother Stephan Simpson posted on social media in tribute to his sister.
“Words can’t describe the pain we’re feeling,” he wrote. “You couldn’t have been a better sister, and I thank you for always being there for me, helping whenever I needed it. A beautiful person whose life has been taken from her. I’ll stay strong, you’ll always be in my thoughts, so please keep watching over us. I love you more than you can possibly imagine. Rest in peace Kelly.”
Detective Chief Inspector Mick Norman said: “This is a horrific incident in which a young mother has lost her life and her child is critically ill.
“Our sympathies go out to her devastated family. They are being supported by specially trained officers following this awful event.
“A large crime scene is in place, and is likely to be in place for some time.”
The Mayor of London Sadiq Khan described this weekend’s string of attacks as “senseless and horrible”, adding: “I am in close contact with local leaders and the Met police, who are working tirelessly to stem this scourge of violence.