I don't want to start another topic, so I'll leave this - an excellent response from a user on Quora on the topic: http://www.quora.com/Parenting/Is-Amy-Chua-right-when-she-ex...
she seems to be blaming her mother for driving her sister towards depression and suicide. Kinda harsh. Could have been something else.
She may never know "why" the depression happened (as if there needs to be a reason) but unfortunately she probably has a pretty good idea of why her sister didn't turn to family for help.