Who is Marta Hallard from The Daughter of Time and what is their importance?

Marta is a friend of Alan Grant's who comes to see him, bringing him flowers and books while he recovers in the hospital. She is attractive and well-dressed, and very vain and conscious of her looks and speech. She is truly a good friend to Alan, having adopted him as a "spare escort" some time ago. Marta is attentive to Alan's need for something to occupy his mind and dutifully finds him books he wants to read. Marta is the one who brings pictures of faces to Alan Grant and encourages him to solve a mystery no one has ever solved before. She is currently in a long-running play called At Sea in a Bowl, and a fellow-actress, Atlanta Shergold, introduces her to her American boyfriend, Brent Carradine. Carradine teams up with Alan Grant on solving the mystery of Richard III.