She had over one million followers on her Instagram account and was considered a social media influencer.
Louis' six siblings (from left) Felicite, Lottie, Phoebe, Daisy and Ernest.
An ambulance was called to her home in Earls Court, London after she collapsed, and paramedics pronounced the 18 year old dead at the scene after attempting to revive her.
Her death comes shortly after Louis released a new song titled "Two of Us" about him and his mom which included the heartbreaking lyrics: "You'll never know how much I miss you/the day that they took you/I wish it was me instead".
Louis has not spoken publicly about this devastating news at this time.
McFadden wrote: "This is so sad".
Family pictures show the singer with his fours sisters who have been supporting each other through hard times following the death of their mother. "Love to you brother I'm so sorry and my prayers are with you".
Her last post was just four days ago.
The siblings' mother died at the Royal Hallamshire Hospital in Sheffield on December 7 2016 after being diagnosed with leukaemia earlier that year.