1. of the house does not belong to her or her husband then she has no right of residence to stay theiren.
2. Since her in laws are only asking to get their own house vacated no case can be filed against them. she can only take a plea of lack of alternative residence to prolong her stay therein but no false case can be filed against them.
3. Your relative can though file case for maintenance and provision of proper residence by filing case under PWDV Act against her husband.