The troubled actress is currently at Utah's Cirque Lodge facility - reportedly receiving treatment for "an eating disorder and addiction issues" - and insiders say she is taking her recovery very seriously.
A friend said: "She is totally committed to getting better.
"Demi has a long way to go, but she is getting better. She has many days where she feels great."
Demi - who split from husband Ashton Kutcher in November amid speculation he had cheated on her and was hospitalized last month after suffering a seizure - is so keen to get better, she is considering extending her stay in the clinic.
The source added: "She is on the right path and won't leave rehab until she's ready."
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Since entering Cirque Lodge, the 49-year-old star has reportedly gained 10 pounds and has been eating up to three meals a day.
Earlier this month, Demi's daughter Rumer - her eldest child with ex-husband Bruce Willis - insisted all the family "believe" she will get better.
She said: "Of course the situation weighs heavily on me.
"My mother is on the road to recovery. It's slow going but we believe in her."