Role in the series
Tigerlily and Yuna have a love-hate relationship. Yuna loathes her lazy cousin making her to do all the chores via blackmail or intimidation, earning Tigerlily the "Tiger the Tyrant". Tigerlily hides her harsh nature with a sunny disposition, much to Yuna's chagrin. Whenever she gets the chance, Yuna will return the favor to Tigerlily for her treatment; such as indirectly interrupting her cousin's naptime or making fun of her phobia of lightning.
Although she is harsh to Yuna, she claims she's only trying to be a role-model. Because of this, she blackmails Yuna into doing the chores around the house, because of her bad grades and threatening to tell their grandmother. There are rare moments when their interactions aren't spiteful.
When Yuna and Stitch reluctantly move off to live with her in Season 3, she mellows out a bit and becomes a bit more friendlier, though still forces Yuna to do the chores. Despite their vitriolic relationship, Tigerlily and Yuna (like Nani and Lilo) love and care about each deeply. Yuna is touched Tigerlily actually cares about her, going as far as to hug her. Tigerlily likewise would do anything to keep her cousin safe, even if meant sacrificing something she wanted, though will use these moments of selflessness as another way to get Yuna to do what she wants as a form of repayment.