The most you can hope for is she is required to provide a formal notice of the termination of your tenancy and if you refuse to leave then, she would have to evict you through the courts. Depending on how the local law enforcement people see your situstion, they may take grandma's side here and not accept you are a tenant and aid in your removal Friday.

I suggest you play real nice with grandma and appease her so you don't get to find out which way this will go. I've seen it go both ways but since you have paid no rent (you can't legally pay grandma with food stamps) you
are looking more like a guest than a tenant to me.