When Kate Middleton, who is battling cancer, popped up at Wimbledon on July 14, people were thrilled to see her smiling and hanging out with her daughter, Princess Charlotte. “Everyone was wondering if she was going to appear at Wimbledon, and she did,” a source dished. “It’s nothing short of a miracle that she has fought this disease so well. She looked incredible — so strong despite the fact that she is fighting for her life.” Karwai Tang, who photographed Kate at the match, also praised the princess, 42, for getting out of the house despite battling the disease. “She seemed to look no diffe…