Your mother being a legal heir to her deceased father, can claim her share in his properties as a right.
If the other co-sharers are refusing or not willing to give her share to her, she may file a partition suit agaisnt them and seek separate possession of her share.
Your mother cannot claim a share in your grandmother's own property as a right during her lifetime.
Your mother cannot interfere in your grandmother's activity of transferring her property to anyone of her choice.
Neither you or your mother can send any notice in this regard also it will not be maintainable.