She joins the party when you find out how to get to the third floor of the boo mansion. She helps Mario defeat Tubba Bubba and then officially joins the party.
Lady Bow attacks by slapping the enemy. She can also cloak Mario to allow him to pass through some solid objects. In battle, she can scare enemies off, make Mario immune to most attacks, or slap the enemy with a fan (if you upgrade her with a super block to the ultra mode) to cause a good amount of damage.
Lady Bow has a butler named Bootler.
Lady Bow also makes a brief cameo in Paper Mario: The Thousand-Year Door in Poshley Heights after the player defeats the Shadow Queen.
Lady Bow was the only female Boo until Thousand Year Door, which included two other female Boos, Peeka and Lahla.