Am I a high-functioning bipolar or just mean like my sister says?

See a psychiatrist. One of the symptoms of bipolar disorder can be irritability, aggression, and impulsive behavior, but the disorder is much more complex than that. See other answers in my virtual practice for additional info. You should see a psychiatrist for a full evaluation.
Bipolar or just mean. Friends and family throw "pscyhobabble" and diagnoses around very freely when they just need to work out their difference or face character flaws and grow up. Bipolar does not equal "mean." most likely, you sister is just trying to hurt your feelings by "labelling" you. You would both do best to get facts from the nami [google this] website about what "bipolar mood disorder" really is.