After battling the disease for quite a long time, Gaga has shared a series of tributes on her Instagram.
"Watching one of my best friends in the world show unfathomable courage, strength, and positivity while battling cancer has really changed my life. Thank you Sonja for inspiring me and all of us everyday with your joy.
"I love you so much it brings tears to my eyes just to think of all the years we've spent together backstage running the show, taking care of each other. You are one of a kind."
"I'm in shock that I won't see her again until I pass too. I vow to be a little stronger everyday for her because that's what she would have wanted.
"I loved her. I still love her."
R.I.P Sonja Durham.