“I am absolutely heartbroken over the passing of Shannen Doherty.” the Newsroom alum wrote on her Instagram Stories July 14. “When I was first diagnosed with breast cancer I remembered how she bravely let the world into her journey and reached out to her. We became instant friends- which I honestly couldn’t comprehend at times because watching her on 90210 was everything to me when I was 10.”

“We bonded through a shared battle and a desire to help other women,” she continued. “Looking back on the last text she sent me just a couple months ago, she asked how I was doing and if she could do anything for me… true to form, Shannen was offering her support even though she was in the final stage of fighting this horrific disease.”

Olivia concluded her assertion with a heartfelt message to her late pal. “Cancer is really f–king scary and Shannen faced it with such dignity, strength and grace,” she expressed. “I’m sending all of my love to her mother who was her best friend, hero and champion every step of the way. Fly so high, my friend.”