The runner-up, who was mentored by The Script's Danny O’Donoghue, previously checked into rehab twice as a teenager after an accidental drug overdose. But sources told The Mirror this spell in rehab is not alcohol or drug related.
Bo lost her mother Ros to cancer weeks after 'The Voice' final last year.
Now, a friend has told the paper: “She isn’t being treated for depression and it’s not a nervous breakdown. It’s just a meltdown of grief and mental exhaustion."
A spokesman for Bo, whose dad is the Earl of Cardigan, 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.”
Meanwhile, Bo's 'romance' with mentor Danny during the show was last month dismissed by him as a publicity stunt.
In an interview with Daily Mail, Danny said: "I didn’t deny or confirm the speculation. 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 May, Bo told The Huffington Post UK she feels sorry for the winner of last year's 'The Voice' competition, Leanne Mitchell, because she didn't get enough attention - "the press was all about Danny and me."
Bo said: "There was a lot of press as far as Danny and me were concerned, so that took a lot of it away from her, when she was the one doing the thing that the show was about, which was music.
"They were too busy speculating about the state of me and Danny, which is a terrifying indication as to the state of the industry."