Demi Lovato celebrating 90 days sober

Demi Lovato's mother says she is proud of her daughter for reaching 90 days of sobriety.

Demi Lovato. Picture: @ddlovato/Twitter

LONDON - Demi Lovato (26) has been receiving treatment in rehab since she overdosed in July and her mother Dianna De La Garza says she is "proud" of her daughter for working on her sobriety.

Speaking on Maria Menounos' Sirius XM show, Dianna said: "She has 90 days and I couldn't be more thankful or more proud of her because addiction being a disease is work. It's very hard and there are no shortcuts."

Dianna also admitted she is unsure of what caused her daughter to relapse.

She said: "I can't really say for sure. I really don't know."

Dianna previously admitted she was still "shaken" by the former X Factor judge's overdose, but said her daughter is now "happy" and "healthy" as she works toward her sobriety.

She said: "It's still a really difficult thing to talk about. I literally start to shake a little bit when I start to remember what happened that day. [Demi's assistant called and] said, Demi overdosed. So, I was in shock. I didn't know what to say. It was just something that I never, ever expected to hear, as a parent, about any of my kids.

"I just feel like the reason she's alive today is because of the millions of prayers that went up that day when everybody found out what was happening. I don't think she would be here if it hadn't been for those prayers and the good doctors and Cedars-Sinai. They were the best. I couldn't have asked for a better team of people to save her life.

"She's happy. She's healthy. She's working on her sobriety, and she's getting the help she needs. That in itself encourages me about her future and about the future of our family."