If my mother in law abuse my parents and tell me to forget all feelings about my parents I have then what should I do? Should I be scilent? If I say to her I can not forget them and you can not say anything bad about my parents.is it sin? What will be the best way please show me.she says her prayers daily but her behaviour is not good.All the times she do bad behave with my husband and father in law in front of everyone.

It would help to know what culture and country you live in. In some parts of the world, this is common. I say OF COURSE you don't forget your parents, but you need to be clever about hiding it. Don't say things about how your parents raised children or cooked or felt about the world. The less you say about them, the less she will say about them. Her words are just words. Her words have no power over you or anyone unless you let them. Do not fight about your love and loyalty to your parents. Stay mostly silent. It has nothing to do with sin.
If something happens that is very important to you, stand up to her according to your own beliefs, not your mother's or father's, even if it comes from how they raised you. Do not do it often. Do it politely but firmly. Eventually you will stop being treated like some sort of invasion in her life, and will be respected as an adult with your own mind. But old traditions are difficult to beat. Your husband may consider all this to be normal, so don't complain to him. When she is really wrong, let him know in little ways, one carefully thought out sentence, without a speech. If your parents live far away, you want to be able to visit them.

What does your husband say about his abusive mother? Is she well, physically and mentally? I doubt you change her by standing up to her, or hollering and screaming. Maybe she has always been this way, so lets just start by seeing how the men deal with this woman and emulating them. I suspect they let her rant and rave and go about their own business. Of course you not use to being around her, or feel obligated to listen to her rantings are left short of how to deal with her. Have you asked your parents for advice and counsel in this matter? What advice do they give you?

Are you and her the only females in the house? Do you have children? How long have you been married and was this marriage arranged? Sorry for so many questions just trying to get a clearer picture of your circumstance which sounds very much like an eastern Muslim/Hindi traditional culture.

Please correct me if I have it wrong, because I would hate to suggest anything that would go against the faith, traditions, or customs of your culture. Had you had any dealings with his family before you married? Did you know how she was before you were married? Did you have a choice in this matter?