Thomas Fisher has been given a life sentence after pleading guilty to the manslaughter of the 51-year-old, who worked in L’Occitane in Royal Victoria Place.
The family of the victim has said it was their wish for him to stand trial for murder.
Ms Fiona was found dead at her home in Lordswell Lane, in Crowborough, on April 27, when officers attended the property after her family could not get hold of her.
She was found to have died from a single stab wound to the chest.
Fisher, of no fixed address, was given a life sentence at Lewes Crown Court when he appeared on Thursday [November 1] and will serve a minimum of two years.
This follows his guilty plea of manslaughter on the grounds of diminished responsibility when he appeared in the same court on October 2.
He will only be released if and when a parole board deems him suitable and will remain on licence for the rest of his life.
However, the original charge of murder was downgraded after psychiatrists analysed a diary Fisher kept in the run-up to the incident.
He also admitted fraud, using a Marks & Spencer Mastercard in Fiona’s name, and driving while disqualified.
Ms Fisher’s only other child, her daughter Megan, 20, released a joint statement on Friday alongside the victim mother Dorothy, stepfather Les and her father Alun.
She is also survived by her brother, Simon. Reports at the time of her death she had recently entered a new relationship after splitting from her 52-year-old husband, a former hedge fund sales director.
The statement read: “Six months ago our world was torn apart when we were told that Fiona, our beautiful daughter and mother to Megan, had been brutally killed by her son.
“We will never get over the shock of losing her in such horrific circumstances, but she will never be forgotten by her family, friends and anybody else that had the pleasure of meeting her.
“Today should be closure on this senseless tragedy, but it will never be for her family. This is something we will have to live with for the rest of our days.
“We would like to put on record that although the recommendation by the Crown Prosecution Service was to accept manslaughter due to diminished responsibility, it was our wish for Thomas Fisher to stand trial for murder.
“Our main aim today was to get justice for Fiona.
“She was in the prime of her life and there was no reason why she didn’t have many happy years ahead of her.
“We now request that the family be left alone to grieve in private.”