Threatening of 498a n DV - Please suggest

I got married in May, 2016 in UP and since then the girl lived with us only 1 month (first time 15 days n then 20 days) & rest of the time she lives with her family. She is the patient of mental disorder from 4-5 years which they didn't disclosed to me or my family before marriage. The very next day of marriage her parents told me about her mental disorder. She denied physical relations and asking for more time which I gave. But after 4-5 days of marriage she started blaming with some serious allegations which were absolutely baseless. Her mother came & took her. There was no contact from them for 3 months then we took first step and cleared everything to her parents that their daughter is lying and they agreed that they lied to us and their daughter also lied about all those baseless allegations. After few days they called us and asked to take her back. Again after 20 days, she said I beat her one night (which is totally baseless). She said in front of everyone that she don't want to stay here and her parents came n take her again. Now they are threatening us, indirectly saying that they have spent x amount on wedding (which is far more than actuals). We afraid that they may file false DV or 498a case. Please suggest what all we can do as the precaution of such false cases.