How do I fix a broken dishwasher?

My girlfriend is not doing a great job on cleaning the dishes lately, she leaves small residues. I already attempted a repair and told her “You disgust me WOMAN, why is my dish not shining?? You know how I feel about dirty dishes, next time you will clean them hard and with respect because otherwise I would have to discipline you”. It is still not doing a great job, i tried gently taps on the sides but maybe some parts are lose and need even more shaking and hits. What would be the best repairing procedure in this case?