It is a typical depression, seems to be related to her preganenc

It is a typical depression, seems to be related to her preganency. It is very hard to deal with, and you may have to consult with real doctors, instead of asking around here. The problem is since she is preganent, if you are sure, it is hard to choose any drug for her. So you may have to deal with it for quite a while.
Well, bring her to see a doctor ASAP.