I think you did an excellent job on the character, helmet and other accessories. If you desire to have protuberant lips and large cheeks, that can be a distinctive feature of this character.

If by "mouse" you mean "mouth", you should be aware that it helps to subdivide the mouth greatly (increase the number of polygons) if you intend to allow movement of the lips. One reason for finely subdivided lips and mouth area is allow animation of her face, so she can appear to be talking.

To make the effect as smooth as possible, the fine subdivisions of the lips and mouth should gradually merge into the large subdivisions of the cheeks.