Attempt to encroach land - Neighbour

Hi, Story : Lets call that along the road, there are 3 lands continuously (Land 1 - Land 2 - Land 3) .My father in law and mother in law have a land in Pudur village, Tuticorin. Lets call it Land 3. Land 1 is owned by my mother in law's aunty (1). Land 2 belongs to my mother in law's another aunty (2) who passed away without kids / husband. Aunty 1 (Land1) occupied the land of Aunty 2 (Land2). Now when my father in law started constructing or upgrading his house in Land 3, Land 1 owner argues that she will not let him expand the house unless we leave 2 feets of land space within our own land. She keeps spoiling the construction house. So, i want a guidance in 2 directions. 1. How to stop her nuisance and legally deny her to block our construction within our own land. I think we need to get a suit for declaration to confirm the legal ownershipe of the land. Beyond that what documents we need to get and where to confirm the surveyor's measurement of land properly. If surveyor is not doing his work properly, how do we approach high court to make him do his work properly. 2. Since Land 2 was encroached by Land 1 aunty, we wanted to gather documents and legally not permit Land 1 owner to have ownership over Land 2. What documents we need to confirm this point. Basically we need to scrap Land 2 from Land 1 owner's hand. Thanks in Advance. Muthuraman