Found the following article online, use it to answer the question: What is the full name of the real owner of the dress?  Diana Whitcombe works at her aunt's country inn, but dreams of escaping to London and making her way in society. When chance provides her with the necessary funds, she makes her way to the big city and takes up employment in a hairdressing salon where she befriends French fellow assistant Annette, and moves into the same hostel in which Annette is living. One day Diana spots a kitten in danger on a busy road, and dashes into the traffic to rescue it. Her kind action is witnessed by singer Jerry Dean, who strikes up a conversation and invites her for lunch the next day at the Ritz Hotel. Diana is worried that has nothing suitable to wear to such a rarefied establishment, but is delighted when Annette produces a beautiful dress which she offers to loan to her. Unknown to Diana however, the dress has been stolen by a maid friend of Annette's from her wealthy employer, and passed to Annette for safe-keeping before it is sold to a dealer. Diana and Jerry meet for their Ritz rendezvous. Unfortunately, also present is the Countess Delavell lunching with her theatrical friend Dudley Chalfont, and it is the Countess' stolen dress which Diana is wearing. At the end of the meeting Jerry, explaining that he has to leave to fulfil engagements in Scotland, proposes to Diana and she accepts. Meanwhile, the Countess' maid, aware that she is already under suspicion, steals some valuable jewellery, alerts Annette and the pair take off for France.
Answer:
Countess Delavell