She’s like the Invisible Woman, but only takes care of herself. She disappears and can counter attack, but doesn’t do anything for your team. At times she might summon a dragon to shoot fire at enemies, but again she doesn’t do anything for the team as a whole.
She’s not bad, but having her won’t greatly increase your chances of winning. It wouldn’t make sense to get her unless you’re just a fan of her. Otherwise she doesn’t help you out enough to justify getting her.