Daughter in laws rights over deceased Father in law's building

Dear Sir, My son has been married since 2000. Initially he and his wife stayed with us for 5-6 months but later shifted to a different city and had been staying there. in 2012, my husband died and I am living in my husband's self acquired house with my unmarried major daughter.I understand that things are not going well between my son and daughter in law.Now, my daughter in law (who is very notorious in nature) with her minor son (my grand son), forcibly wants to come and stay in the house I live. I have searched on internet that a daughter in law has no rights on the self acquired parent in laws property. Going by my daughter in law's nature, I fear, she might file false domestic violence or any other case against me and my daughter.I have few questions 1) What can be done to stop her from coming and staying with me? Can we approach police/court in advance? 2)How much right I have on my deceased husband's property (building)? 3)How much right my son and unmarried daughter have on the property (building)