Regarding misuse of marital laws

Sir/madam, my family is very disturbed because of one of my family member. my brother's wife is very much disturbing everyone. all the time she try to control others and if anyone go against, she threatens us for suicide although she is pregnant by 5 months. we all are afraid of her threatening if she really done something with her someday and put blame on any or all of the family members, then what will we do. we are all trying to support her in every way but her attitude is so negative that she is just not ready to understand anything, above all her own family members are playing games sometime they say in our favor and sometime in her, sometime they start blaming us for no reason and sometime says that they know their child is stubborn and doing idiotic things. she is not afraid of anything of any law because her father is working in delhi police. my parents are very disturbed and also suffering from various diseases, i want their peace and a happy old age with all their children. please guide us for legal steps in case she use law against us.