What symptoms lead Lisa's friends to believe that she is manic depressive in the novel, Lisa, Bright and Dark?

Lisa has emotional problems that lead her friends to believe that she is manic-depressive (bi-polar). Lisa engages in self-mutilation, and is sometimes violent. At one point, Lisa exhibits signs of multiple personality disorder (MPD). Her other "personality" speaks with an English accent and makes cruel remarks to those around her. In this state, Lisa loved to "show off [...] to demonstrate how clever she was, how mean and brilliant and in charge" (p. 92). Lisa's behavior frightens and confuses her friends.