The Doves of Venus — Olivia Manning

Pretty, brave and eighteen, Ellie has come to London in search of adventure. She soon finds it in Quintin Bellot, the handsome but tired dilettante who finds her a job in fashionable Chelsea. But Quintin, the seducer of one dove, is also the husband of another. And Petta, his once beautiful wife, is fighting back age as fiercely as Ellie is plunging into it.