Bo, who was runner-up on the first series of the BBC1 singing contest, tragically lost her mother to pancreatic cancer last June - just weeks after the show finished.
The star's mum, Ros, had been battling the disease while 28-year-old Bo was on the TV show and the hopeful divided her time between the studios and the hospital.
At times, Bo slept on the floor of Ros' room on an inflatable mattress so she could be close to her.
Friends now say the trauma of dealing with her mum's illness and the grief that followed in the full glare of the public has caught up with her.
A pal told The Mirror: "She had to grieve her mother's death in a very public way.
"It is a delayed reaction – almost like she was sleepwalking for a year-and-a-half."
During her time on the 2012 series of The Voice, Bo - real name Lady Catherine Anna Brudenell-Bruce - was romantically linked to her mentor Danny O'Donoghue.
It was never confirmed as whether anything happened between them, and Danny recently said: "I found it funny.
"By not saying anything, it created its own buzz. I thought I'd use it and help Bo get publicity."
In response to the rehab reports, Bo's spokesman said: "A lot of things have caught up with Bo which she never got a chance to deal with because she got thrown straight into the limelight after The Voice.
"She'll be bouncing back very soon."