What should I do if professor grades unfairly?
Two steps:


Ask her for a meeting in her office where you can talk in peace and
phrase your concerns in a friendly but clear way. First say that
your feeling is that there is a problem but you are not exactly sure
what it is and why it is there. Then ask what you can do to improve
the situation. Don't make any accusations ("You grade my papers
worse!!") and dont get personal  ("You don't like me!") that will just make her defensive. Rather say
things like "I feel that something in our communication is not quite
optimal and I am here today to ask what I could do to improve the
situation.".
If this meeting does not improve the situtation then you will need
to go higher up in the food chain and talk to whoever this is.