Andrea Gada, of Downland Close, Eastbourne, was struck by a Ford Fusion in Friday Street in the town at about 15:15 GMT on Tuesday.
She was airlifted to St Georges Hospital in Tooting, south London, but died from her injuries on Wednesday.
The 64-year-old female driver from Eastbourne was not injured in the incident, Sussex Police said.
A five-year-old girl who suffered "life-threatening injuries" when she was hit by a car in Sussex has died.