Furious Demi Lovato has fired off at Internet trolls who took aim at her 12-year-old sister over the weekend (30-31Aug14).

The singer was horrified and appalled by comments targeted at her "baby sister", actress Madison De La Garza, who suffers from scoliosis, and she took to Twitter.com to attack the sick individuals who thought her condition was something to make fun of.

She raged, "For anyone telling me to 'chill'... The impact bullies have over the internet can lead people to suicide.

"I can handle the bulls**t. But do NOT f**k with my baby sister. I'm all for peace and spreading love UNTIL you go after a 12 YEAR OLD who did NOTHING to you... So disappointed that after all the conversation about cyber bullying in this world that people would continue to do this to others.

"@Maddielovesyou1 you are BEAUTIFUL and the most precious little angel in my life and I will always protect you. I LOVE YOU."

She added, "Physical disabilities are NOTHING to joke about. SEVERE SCOLIOSIS IS NOTHING TO MAKE FUN OF."