That's kind of WFT's game- she dances around waiting for the opponent to make a mistake and then capitalizes with great speed, and can try to create opportunities with sun, ball, and breathing. Best approach (or at least the one that works against my WFT) is to just be patient- keep the pressure on, and don't get frustrated. Outside the two projectiles, WFT has little range and the projectiles are both pretty well telegraphed, don't let them get in your head. Also, her hitboxes are wonky, and you should know where you aren't safe (behind WFT, for instance).
I think WFT is highly underrated, and like other decent characters, the best way to learn the matchup is to learn more about the character.