Winning a point is a very low bar. You don’t have to beat her. You don’t have to win a set or a game. You just have to score a single point. All it takes is a single mistake from your opponent to win a point. With enough time even the best will make a mistake, and tennis matches are long.

The shortest possible game is 4 points. A set without a tie breaker has 6 games. A women’s tournament match is best 2 sets of 3. So at minimum a match of tennis has 48 points. You only need one.

If you’re passible enough to return the ball some of the time, and do a valid serve you will probably win a point at some point. She may be one of the best tennis players of all time, but she’s not infallible. Its really unlikely she wouldn’t mess up at least once.