How to handle depressed. Plz help me.

I was married 4 years back and from starting I feel my wife is ultra sensitive. She will get upset very easily and will use offensive words with anybody. There were occasions when my parents would have told somethings a bit assertively and she has taken those things very badly. Initially she had full trust on me and my relation with her was good. But from the time I have started supporting my parents as they are also interested in ironing out differences, my wife lost trust in me. She becomes violent at times and speak harsh words. If we try to reply assertively she will get further violent. After the last incident when she suddenly slapped me and warned me of commuting suicide, I think she is suffering from depression. I want to help her but she will not cooperate. Plz help me.