What does she say/do that makes you specifically think she is mean?
Instead of worrying about what she is doing, you should be thinking about what you are doing. Teachers REACT to student behavior. Therefore, there is probably something you are doing that angers her. Are you doing your work, staying quiet (except for class discussion time), helping around the classroom during cleanup, waiting politely for help and asking courteously, etc.?
If your HONEST answer to each of the above is yes, you are hard-working, courteous, and helpful, then look at the overall class behavior. Are there people who are just absolutely driving her nuts? If that is the case, talk to her about your feelings when she yells at everyone when it's only a few people... and time when you are going to talk to her carefully. Wait for a moment when she smiles when she sees you...lol!
If all the students are courteous, hard-working, and helpful, then she's stressed out about her colleagues or her private life. Talk to your parents about your feelings, and remember that the end of the school year is very soon!