There are a couple of ways this can be viewed. I like to view it as an enforcement issue.
If she calls the police and tried to have you removed the police will ask to see some identification like a driver's license. If the grandma's address is on that id, then they will not force you out.
The next enforcer would be the court. If she files an eviction will they force you out. Not likely without notice. These things take time. It certainly would not be over night, or immediate.
--Sale of the property--
If she sold the property they would likely still need to have you evicted.
--Power of Attorney--
Power of Attorney requires that the person be of sound mind to over see. So, the type of power of attorney would be very important in this circumstance. You probably need to get a copy of the document and go see an attorney to figure out how to proceed.
Specifically, the question is whether you have rights, so I will direct my answer to that. Assuming that the power-of-attorney is valid, the daughter has the authority to demand that you leave. If you refuse, she will have to prosecute an eviction action against you. You have the right to notice of hearing, and the right to present any evidence suggesting that you are not subject to eviction (such as a written lease that has not been breached). It is very difficult to defend against an eviction, though, unless you have such documentation. The best course of action would be to start looking for a new place to live.
This is a complicated situation. The daughter would have to evict you and I have some ideas as to what you can do in the interim. Feel free to call me.
Cheryl P. Baraty
Baraty & Polansky
This is advice only and not a legal opinion on which action should be taken.