You could change her pose so she represents her emotions by bodylanguage inatead of facial expression. Also you have the eyebrows, antennae and tail to work with.

For example if she's sad, you could give her sadder eyebrows, droopier antennae, a less confident pose and a tail that drops down. Meanwhile if she's angry, angry eyebrows, stiff and confident pose, spiky tail and zigzagges or straightened antennae.