Stephanie Curtis, 35, from Blaenau Gwent, was driving a blue Peugeot which was in collision with a silver Mercedes on Thursday.
Ffion Elizabeth Merrifield died after the crash while her mother died later in hospital.
Two women in the Mercedes both suffered minor injuries.
The crash happened on the eastbound carriageway between Brynmawr, Blaenau Gwent and Gilwern, Monmouthshire at about 1100 BST.
Ms Curtis died of her injuries at the University of Wales Hospital in Cardiff.
The mother and daughter were from the Nantyglo area of Blaenau Gwent.
All involved in the crash were initially taken to Nevill Hall Hospital, Abergavenny.
Gwent Police said the Mercedes was being driven by a 69-year-old from Gilwern. Both she and her passenger are still in hospital.
The A465 was closed in both directions between Gilwern and Conoco roundabout at Brynmawr while emergency services were in attendance.
Gwent Police is investigating the collision and anyone who may have witnessed the collision is asked to contact the force's collision investigation unit on 01633 642404 or by dialling 101.
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