J.K. Rowling (left) and Serena Williams (right)  07/11/2015 AT 02:10 PM EDT  has no time for the haters – especially if their target is her friend.  author fired back at a Twitter user on Saturday who had harsh words for six-time  The 49-year-old first shared a photo with the tennis champ on Saturday, showing her support of Williams prior to her Women's finals match.  "I'm #TeamSerena today, because you don't meet many super-talented people nicer than she is," she wrote. "Go @serenawilliams!"  I'm #TeamSerena today, because you don't meet many super-talented people nicer than she is. Go @serenawilliams! pic.twitter.com/KHDYNCt6Ls  After Williams won, Rowling continued to show her support through another Tweet, writing, "What an athlete, what a role model, what a woman!"  #SerenaSlam! I love her. What an athlete, what a role model, what a woman!  One Twitter user's reply, however, left the author up in arms.  "Ironic then that main reason for her success is that she is built like a man," the user wrote to Rowling.  "Yeah, my husband looks just like this in a dress. You're an idiot," the star wrote back, sharing a photo of Williams clad in a red shift. Game. Set. Point – Rowling.  .@diegtristan8 "she is built like a man". Yeah, my husband looks just like this in a dress. You're an idiot. pic.twitter.com/BCvT10MYkI  Williams's Saturday win completed her second "Serena Slam" – winning four Grand Slam tournaments in a row, starting with last year's U.S. Open, then the Australia Open, the French Open and now Wimbledon.  Williams won 6-4, 6-4 on Centre Court at the Wimbledon Women's finals against Spain's Garbine Muguruza.
The Harry Potter author fired back at a commenter who wrote that the athlete had the body of a man