Fuu... Talk about an aim at moe by the developers. Goth Loli + Gruesome book + Mascot (that moves)
Yeah, she is pretty cute, but her lines are also very amusing. Just because she's all smiling while saying horrible stuff. But she also says some cute stuff. But in general, she says some mean things seemingly without evil intent(?).
Also, it seems she as a summoning cost, because Exile did not work on her (see Level-Up Stage)
As an opponent, she has some pretty strong cards, such as Meteor and Evil Blast. Her book is mainly filled with gruesome or dark cards, such as Ghoul, Binding Whip, and Vampire.
And they are strong cards.
But on the other hand, her book is really heavy, with plenty of summoning conditions and plenty of discards. Try placing down Gold Idol while fighting with her. You'll see she suddenly gets that much more stronger.
Below are some lines she says in-battle. There are plenty more, but these are just some examples I was able to take before I got tired. If you can't read the Japanese... Well, at least enjoy her artwork.