Ms Fox said she was at Heathrow Airport preparing to fly to Spain in November 2024 when she found out Bowen would be released again.
Ms Bowen, 53, disappeared from the home she shared with her husband in Llandogo, near Monmouth, in August 1997.
Her remains, tied to a kitchen sink, were found washed up on the banks of Wentwood Reservoir, near Newport, in February 2017.
Bowen, 72, who now goes by the name Raymond Bowen, refused to tell police where Sandie’s body was and has never admitted her murder.
Court documents seen by Wales now reveal Bowen was regarded as high risk at the time of his initial release in 2015.
Ms Fox said this meant Bowen should not have been released.
“He took away my mum, my opportunity to grow old with her and for my grandchildren to meet her,” she said.
“I’ve never had what I would say is real closure, because he’s never, ever admitted to murdering my mum.”
