Blanca

Blanca serves as Vanilla's magical familiar. She is a mouse who dislikes being referred to as a rat. She is extremely helpful to Vanilla, offering advice on how Vanilla can acquire more hearts. She loves Vanilla, openly dislikes Chocolat, and frequently laughs at Chocolat's plans. She appends "-chu" to the end of her words, a mannerism that is mouse-like in Japanese.
In the manga

Spoiler

Her real name in English is Libbie/Libby, and Blanca is Spanish for white (the feminine form of blanco).