1. After the will made by your maternal grand mother during her life time in favour of your mother the latter became the owner of the property on the demise of your maternal grand mother.
2. Your deceased maternal uncle's widow can be evicted by your mother by filing a suit for her eviction in the court. Police has no role to play in this. The only legal recourse available to your mother is before the court.
3. Once your uncle's widow is evicted your mother can execute a deed of relinquishment or gift deed in favour of her younger brother to transfer the ownership to him.