My mother isn't getting her flat possession even being the title holder of the property

My mom is the owner of flat in kandivali west Mumbai , she had taken this flat from mhada in open sale in 2004 , 2012 she had given her flat keys to tiwari who was residing in the same building as he had helped her at that time for money and told her that that he would purchase it and would give her the amount and after giving amount she can get the agreement registered and transfer the flat but before that he handed over the flat someone else we didn't even know that person, he is residing in the flat from last four years , when my mum before 4 years tried to be in the house get in the house as she had the key but the person forcefully registered and trespassers FIR on my mum and police warned her not to go back to that building again or she could be arrested being a senior citizen she was so scared that she couldn't take any step. Now after many notices society has put her name on board and allow her to pay the maintenance as well as have given a letter stating that they don't know who is residing in the flat . mhada has also given a letter in 2020 stating that she is the the owner of the flat and the title is on a name , even after so many problems we are trying to find a way to vacate the premises peacefully . Mhada has also stated in the letter which was given in 2020 to society to take legal action on treaspasser who is inside the flat , but society isn't helping us in any way . We are not Capable to pay Court fee and my mom doesn't have a son . She is 67 yrs old now and going to court for her own case in which she is the trespasser in her own flat .