Holly Marie Combs Says a 'Part of Me Is Missing' Following Shannen Doherty's Death: 'My Better Half'

Holly Marie Combs is mourning the death of her "better half."

Following Shannen Doherty's death on July 13, her former Charmed costar reflected on their decades-long friendship in a touching tribute on Instagram.

Combs, 50, shared a carousel of ten photos of her and Doherty, who was 53, dating back as far as the '90s hit show, as she called the late actress her "best friend."

"My better half of 31 years," she shared. "There is a hollow in my chest and I can't seem to catch my breath. A part of me is missing even though I know exactly what you would say to me right now. I know exactly what you would tell me to do right now."

Combs reflected on how Doherty's legacy will continue on in her sons, Riley and Finley, saying, "I know your undying spirit will live in me and my kids who you loved as your own. They will walk with your sense of purpose and pride. They will be truthful and stand up for what is right. No matter what and zero f---s given. Your fire will live on in them and the many other Charmed ones you helped raise."

Calling the actress "a fierce fighter til the end," Combs concluded her post, "My most ardent champion. My loyal protector. My best friend. You taught me the meaning of family. You were and will be forevermore my sister. I love you."

Doherty died on Saturday, June 13, after years of living with cancer, her longtime publicist Leslie Sloane confirmed to PEOPLE.

"It is with a heavy heart that I confirm the passing of actress Shannen Doherty. On Saturday, July 13, she lost her battle with cancer after many years of fighting the disease," Sloane said in a statement.

"The devoted daughter, sister, aunt and friend was surrounded by her loved ones as well as her dog, Bowie," Sloane continued. "The family asks for privacy at this time so they can grieve in peace."

Combs' tribute joins an outpouring of support from the Charmed cast with Alyssa Milano and Rose McGowan also mourning the loss of Doherty.

In a statement to PEOPLE, Milano, 51, said, "It’s no secret that Shannen and I had a complicated relationship, but at its core was someone I deeply respected and was in awe of. She was a talented actress, beloved by many and the world is less without her. My condolences to all who loved her.”

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McGowan shared a lengthy tribute on Instagram as she praised Doherty for having the "heart of a lion."

"Passion for craft is often mislabeled as trouble. Shannen was passion. I met her in the 90s and was awed. Getting to really know her later in life, a beautiful gift," McGowan, 50, who entered the show after Doherty's departure in 2001, wrote.

"This woman fought to live. Shannen knew how to be a star because she was one since childhood. Her work ethic inspiring to the end. Shannen’s great love for directing, for acting, Holly, her friends, her parents, dog and her beloved fans was legendary. Our lives had been intertwined in a unique way. We laughed at dark forces who wanted us to hate each other, instead we chose love and respect. A soft-hearted badass as there ever was. A force of energy that will live forever in hearts."