When she was winning she was known as a player that was strong mentally with a killing instinct. That was the reason given by Jim Parsons (The Big Bang Theory) on why he had become her biggest fan. But that's all gone now. Her confidence is shot and you can't win in tennis if you don't have confidence in your abilities.
She played okay in her first set the other day, only to lose in a tie-breaker. But once she was down by a set, it seemed that she totally gave up and barely showed up for the second set. A few years ago when she was at the top of her game, she wouldn't have let being down by one set get to her. She would have used this to motivate herself into upping her game and snatching victory from her opponent.
From all accounts she looks great in practice. But as soon as she hits the court, her confidence disappears as the unforced errors start piling up. Who knows, maybe she needs to take a year off from the game and re-evaluate her life.