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.
Tennis isn’t played one game at a time. It is played one match at a time. Any point is one point in a game.