The Cool for the Summer singer's pal Marissa Callahan's mother is fighting the disease, and a page on the GoFundMe fundraising website has been set up seeking $10,000 (£8,180) to help the family through the health crisis.

Demi used her Twitter account to promote the campaign, writing, "Please help support my best friend and her family through this extremely difficult time. I love you Marissa."

The GoFundMe page, which was set up by another of Marissa's pals, Kelsey Kershner, contains a picture of Marissa with Demi.

A message on the page reads, "Marissa's amazing mom has recently been diagnosed with breast cancer. Please donate in any way you can. Every bit counts! Let's show Marissa and her family how much love and support surrounds them during this time."

Well-wishers had donated $1,728 (£1,410) of the $10,000 in funding sought at the time of WENN going to press.

Earlier this month (Oct16), Demi announced she would be taking a break from music next year (17), telling fans that she's not "meant for this business and the media".

Her decision to move out of the spotlight came after she was targeted by Taylor Swift fans on social media due to comments she made in an interview with Glamour magazine about the Shake It Off singer.

In the interview, Demi criticised Taylor for her feud with fellow pop superstar Katy Perry, accusing her of, "tearing Katy Perry down".

Demi refused to apologise for the comments, writing on Twitter, "Also don't forget that words can be taken out of context when doing interviews.. still not apologizing for saying what everyone want to say (sic)."