Born to Sir John Ashley Mullens, a stockbroker, and Evelyne Maude Adamson, Elvira had a privileged upbringing. She studied drama under Constance Benson at Lady Benson's Drama Academy and performed in the musical "The Blue Kitten" at the Gaiety Theatre during the 1924–25 season.

In 1928, Elvira married American singer John Sterling Barney, but the marriage was short-lived as John returned to America the following year. She then became involved with Michael Scott Stephen, a relationship marked by turbulence and substance abuse.

On 30 May 1932, after hosting a dinner party at her Knightsbridge home, Elvira and Michael had a heated argument, culminating in Michael being shot dead. Elvira was arrested and charged with his murder. ​

The trial commenced on 4 July 1932 at the Old Bailey and garnered significant media attention. Elvira was defended by Sir Patrick Hastings, who portrayed her as an innocent party ensnared in a tragic accident. Witnesses, including Wade and Jeffress, provided testimony. On 5 July 1932, the jury acquitted Elvira of both murder and manslaughter charges but found her guilty of possession of a firearm.

Following the trial, Elvira's family distanced themselves from her, prompting her move to France. Her lifestyle remained tumultuous, marked by excessive drinking and alleged drug use. On 25 December 1936, Elvira was found dead in a Paris hotel room after a night of heavy drinking.