The accident happened on Route 9 and Madison Street at 8:44 p.m. Sunday.
Police say 53-year-old Gary Episcopo of Delaware City was driving a 1992 Toyota Corolla when an antlered deer walked into the path of the vehicle.
The impact sent the deer through the windshield, hitting 48-year-old Jamie Episcopo in the front passenger seat.
She died on Tuesday from her injuries at Christiana Medical Center.
Gary Episcopo was not hurt.
This is the height of deer mating season.
They are more likely to be out near and crossing roads to get to each other.
The State Game Commissions is urging drivers to stay alert.