Followup question on biting, scratching aggressive toddler....child psych ideas?

I have a little cousin who sounds like they have similar behaviour (but not quite as harsh ) but still similar, he just got diagnosed with manic depressive or bi-polar , his father is the same way. That might be something to check out. She sounds like she goes from one extreme to the other like manic-depressives do. You can get proper meds for such an illness. Its more about a chemical imbalance that makes people react certain ways. Worth a try. Fingers crossed for your friend!