The 22-year-old actor has been dating Coker, who was the assistant producer on three `Potter` films, for a year now.
Coker`s father Malcolm has given his approval and a friend of Radcliffe said that he is considering marriage, reported Sun online.
"They`re crazy about each other. Dan wants to marry her," said a friend.
Coker, 22, met Radcliffe while working as a production "runner" on `Harry Potter and The Deathly Hallows Part One`.
Film chiefs worried about the schoolboy wizard`s image ordered the affair to be kept under wraps until the last Potter film.
But the actor recently let it slip when he said, "I`m very much in love."