The 49-year-old actress - who was hospitalised last week after she suffered a seizure - is reportedly "on total lockdown" at the 1,000-a-night Cirque Lodge addiction treatment centre in Sundance, Utah, where she is said to be receiving treatment for "eating disorder and addiction issues".
A source told E!: "She`s on total lockdown and only talking to a small group of people."
Demi - who split from husband Ashton Kutcher in November amid speculation he had cheated on her - is recently thought to have been struggling with the fact that her troubles, which are rumoured to include anorexia and substance abuse, have been under so much scrutiny which has led to her seeking help.
The source added: "It became clear to her that her way of coping with her stress was not working and she needed more help."
Last week, Demi`s three daughters, Scout, 20, Tallulah, 16, and 23-year-old Rumer, as well as ex-husband Bruce Willis, were said to have encouraged the `Striptease` star to professional seek help, but she reportedly refused to go to rehab.
Ashton Kutcher is also thought to have urged Demi to go to rehab following her hospitalisation.
A source told RadarOnline: "Ashton has had loved ones in his life that have dealt with addiction issues, and he realises that it`s counter-productivefor someone to be forced to go to rehab.
"Ashton knows the addict has to want to get help for themselves. There is a lot of noise around Demi right now, and Ashton wants her to know he is there for her and supports her no matter what."