Fawcett died at a Santa Monica, Calif., hospital at age 62 after a nearly three-year battle with cancer.
"There are no words to express the deep sense of loss that I feel. For 30 years Farrah was much more than a friend, she was my sister, and although I will miss her terribly, I know in my heart that she will always be there as that angel on the shoulder of everyone who loved her," Stewart, who reportedly was with Fawcett when she died, said in a statement issued to Usmagazine.com.
Fawcett's "Charlie's Angels" co-star Kate Jackson told the magazine she will "miss Farrah every day."
"She was a selfless person who loved her family and friends with all her heart, and what a big heart it was," Jackson said. "Farrah showed immense courage and grace throughout her illness and was an inspiration to those around her. When I think of Farrah, I will remember her kindness, her cutting dry wit and, of course, her beautiful smile."
Jaclyn Smith, also an "Angels" veteran, said she, too admired Fawcett's fortitude.
"Farrah had courage, she had strength, and she had faith," Smith said in a statement to Usmagazine.com. "And now she has peace as she rests with the real angels."
Luxury accessories designer Lana Marks described Fawcett as a "much loved friend, a dazzling beauty both inside and outside."
"I will cherish our time spend together and will miss her," Marks said in a statement.