Legal Question in Real Estate Law in Massachusetts

This sounds like an invitation for a costly legal dispute down the road.

One circumstance where your sister may be permitted to transfer the property from your mother to your sister, as trustee for your mother, is if your sister has a valid power of attorney in her favor executed by your mother.

Assuming that your mother has full capacity, your question raises serious questions. I would address this immediately while your mother is able to express her wishes and intention with respect to the property.