Dowry and domestic violence

It is about my sister we married her before three years but since then they are saying to her that yours parents had not spend enough money. your family is cheape due to you and your family we have to face humilation in our relatives and our society. we tried fulfill there demand as much we can but situation got even worse they started to torture her mently by diffrent ways and at last i brought her at our house before 5 months. and then we tried to solve this situation we met many of their relatives and other reputed people of the area to make situation better. but nothing went right. now they are saying that we will not allow her to enter in their house again they are demanding divorce. so what can we do now leagly. 1) whatever they did. they did at their home and how can we prove that we have no evidence and in front of other people they sey everything is false allegation. 2) she is at our home from last 5 months. can it will go against us or it will make our case weaker people are saying that you should had done it at the same time now you have spent lot of time and now it is their favour. 3) my sister dont want to get divorce. i have one more sister and she is unmarried it will create problem in her marrige to so what should we do now. please reply thanks amit