Because, people say she is cute and dislike her but they are just trying to say they like ami and hate her. So more people dislike her because she's not cute and like her because she's cute but most not everybody likes ami they say usagi's the best character in sailor moon and that's true!
Because Ami is the most intelligent of the Senshi. She was often a fun killer talking about school. In the fight against the DD girls she herself said that her attack are useless against them. Thought did she die and got stronger later on when the girls went to the new school did many call her a jerk when she said the name of the file that she printed out for a boy out loud. They looked at it like she was mocking him because he didnt understand english and wanted to become engineer.