Police were called to the property in Rectory Road, Hackney, around 10.15pm on Thursday, and arrived to find the victim had been stabbed several times.
She was tragically pronounced dead at the scene, shortly after 11pm.
A 37-year-old man has been arrested on suspicion of murder and remains in police custody.
Detective Chief Inspector Mark Rogers, leading the investigation, said: “This is an incredibly sad incident and my thoughts are with the victim’s family and friends at this unimaginably difficult time.
“I want to reassure them and residents who will be shocked by what has happened in their community, we are working hard to establish what has happened.
“Anyone who witnessed anything out of the ordinary or has any information about this incident should contact police as soon as possible.”
Anyone with information is asked to call 101 or Tweet at MetCC with the reference 6902/15DEC.
Alternatively, contact the independent charity Crimestoppers anonymously on 0800 555 111.