I think she's playing it up.
Consider that she was absolutely crushed yesterday. If she had merely failed like any other athlete, it would have reflected poorly on her. Therefore, she flips the script.
It's a playbook she's used before. By calling out the heckler and addressing the audience, the story changes from "world class player falls short yet again" to "world class player, through no fault of her own, is sabotaged by the fans/the press/the tournament/her own mental health struggles (pick one)." What's better, she implicitly establishes herself as the true heir to the Williams sister and their legacy in the process.
So, in short, she failed at tennis, but succeeded wildly at changing the narrative, manipulating the media, and protecting the brand. It's very clever.