Beside the photo, Bella shared an incredibly sweet message dedicated to Yolanda: "I am also SO proud of my mom @yolanda.hadid today and everyday," she wrote. "This book marks such an incredible day for you. I have seen you in bed, struggling for the past 5 years of our lives, thinking to myself 'why would this happen to such an angel?'"
St. Martin's Press
She continued, "I would cry to myself knowing that there was nothing I could do to help and that there were people going against you and what you are/were going through. Incidents where you would be so sick, not being able to move your bones/body, and I would have to drive you to the hospital at 3 am so I could see you get a shot of something just like every other day you would have to do treatment. You have been in more doctors labs and testing rooms every SINGLE day, then I have ever seen in my life... To find a CURE for people around the world."
Bella also touched on her own struggle with the disease.
"I have been struggling with Lyme and other co-infections for the past two years which has debilitated me from riding my horses, going to school, and struggling with work which are all the things I am so passionate about," she admitted. "You are the only person that would believe me and understand what I was going through. This book shows Kids and adults with Lyme across the world that you are not alone and we believe you!"
Meanwhile, Yolanda announced on Wednesday that she would be leaving The Real Housewives of Beverly Hills in order to focus on her recovery.
"I would have loved a more graceful exit then 'Season 6' but sometimes we don't get to control the endings of the chapters in our life," she said in a statement on Instagram. "I am leaving what's over without denying its past importance in my life. I believe that every exit is an new entry and with that in mind I say goodbye to my@Bravotv Family as I continue to focus on a my recovery and bring back the privacy within our home."
She concluded, "Thank you to all the fans for your love and unwavering support these past 4 years. I am grateful for the housewife experience and all it has thought me. I'am excited about this choice and look forward to the next chapter of my life."