Concern about a friend: how common is in women to having manic episodes in self medication with zoloft (sertraline)? she's very impulsive and aggressive lately.

Can easily happen: No one with a psychiatric condition should self treat. Sertraline is for depression. It is not the primary treatment for bipolar disorder. It can in fact worsenbipolar disorder by increasing the frequency of the episodes, severity of mania, causing mixed mood states, or rapid cycling. As a friend, please pull her aside and tell her what you were noticing. Show her this reference if you need to and try to get her to a psychiatrist. Best wishes.