Emmeline Vance was a member of the Order of the Phoenix, both in the 1970s and in the 1990s. She was part of the Advance Guard that escorted Harry from number four, Privet Drive to number twelve, Grimmauld Place (OP3, OP9). She is described as a stately-looking witch with an emerald green shawl.
She was brutally murdered by Death Eaters in the first weeks of the Second Wizarding War (late June or early July 1996) (HBP1); Severus Snape claimed to Bellatrix that he was the one who betrayed her (HBP2). Murder occurred near number ten Downing Street, London (HBP1).
Emmeline = Medieval pet form of Emma. This is the name of the central character in Jane Austen's novel Emma, which is JKR's favorite novel.