She had been strangled by her attacker, who police believe had been intending to steal from her as she slept.
Emmy was taken to the Theresienstadt concentration camp in 1942.
A 16-year-old boy was arrested within a few weeks of the murder and charged but was acquitted at the Old Bailey in February 1973.
The Met Police said officers were now taking a fresh look at Emmy's murder in the hope the passage of time may provide some clues and encourage people to come forward.
A reward of up to £20,000 is being offered for information leading to the arrest and prosecution of her killers.
Before World War Two, Emmy, her dentist husband Albert and their daughter Hedy lived a comfortable life in Brno, Czechoslovakia, until the German occupation in 1939.
In 1942, she was transported with Albert and Hedy to the Theresienstadt concentration camp near Prague.
In October 1944, Albert was taken to Auschwitz and then, as the Allied troops advanced, on to Kaufering concentration camp where he was killed in February 1945.
Emmy and her daughter, then aged 17, were liberated in May 1945 and moved to London in September 1946.
They lived with relatives before settling in the Finchley area.
Emmy suffered from mental health problems for years due to her war-time experiences but eventually made progress through treatment.
She moved to a residential care home in Finchley but visited her sister in central London regularly, staying at Queens Hotel.
On the evening of Saturday, 16 September, she had been to Vaudeville Theatre on the Strand with two friends to see Move Over Mrs Markham, before settling for the night at her hotel.
Detectives believe she was attacked in her room in the early hours of the following morning and the most likely motive was theft.
Emmy's granddaughter Carolyn Franks, 58, described her grandmother as a "vulnerable woman".
"No-one should have to die like she did, especially after the trauma she had already endured," she said.
"The effect on her close family continues to be a source of great sadness to us and we feel whoever killed her should be held to account."
Officers hope to trace people who used to work in or visited the hotel around the time, who were mostly of different nationalities, including German holidaymakers and Swedish staff.
Det Insp Susan Stansfield said: "Although many years have now passed since Emmy's death it remains particularly difficult for her family that she survived the horrors of the Holocaust yet died in such brutal circumstances.
"The hotel served a mixture of guests and employed a number of staff who were spoken to by police at the time.
"However, with the passage of time, it is possible that the events of that night have since been discussed and there is information that could be really useful to our inquiry.
"Did you stay or work at the hotel or in the area of Inverness Terrace, west London, in the early 1970s? Has anyone told you anything in confidence that you feel you should now disclose to police?
"We would also be interested in speaking to the friends - one from the hotel and an Italian woman - who Emmy went to the theatre with that night in case they have any useful information."
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