Emergency services were called at 1.58pm to reports of a blaze in a flat on the 11th floor of a 17-storey building in Hillingdon Street.
Ambulance crews, including specialist units, arrived within minutes.
Ten fire engines and around 70 firefighters were sent to the scene.
The fire was brought under control shortly before 3pm.
London Fire Brigade said the flat was completely alight on arrival, but the woman had left the property before crews arrived.
Station Commander Tony Perks said the fire was highly visible and caused disruption in the area.
He advised people to continue avoiding the scene while crews damp down remaining hot spots.
The cause of the fire is under investigation.
