Rockstar Table Tennis

Easiest way I got "THIS" achievement was like this.
I went to game options, set Games per match: to 1 of 1,
Points per game: to 7
Started an exhibition match on EASY... then I picked my favorite character (Jesper) against someone I hated (Kumi). Each game should take less than 2-3 mins to complete. After each game, I kept hitting rematch and got to 40 wins in no time. Have fun...

Win 40 matches against the computer in exhibition or tournament on any settings.

You can unlock her by winning a set 11-0.

There are two ways to unlock this achievement and ill explain both.

#1 play the rookie circuit
When you reach Cassidy you need to shut her out. Have the setting set to 1 game, 7 points per game. She isn't very good and you can shut her out 7-0.

#2 Longer method but still works.
Win 40 matches against the computer in exhibition or tournament on any settings.
Also set the games to 1 of 1 and points to 7 a game.

For the people who don't know how to change the game settings you will need to go to the game options on the main title screen and change them there.