Groom`s Mother Involvement

My future mother-in-law is driving me crazy with what she thinks she is to pay for. Her biggest concern is that she think that she will need to pay for the hotel says of the wedding party that is out-of-town and the guests as well. I have tried to tell her that all she needs to do is have a section of rooms blocked off in a hotel and that is it. Everyone that will need a room pays for it themselves. After saying this, she still thinks that she will need to pay for the wedding party. Again, I told her that it is not her responsiblity. Besides, the only ones in the party that will need a room are the best man and his wife who is also in the wedding and the grooms parents. I am not sure what the big deal is and how to go about telling her that it is not on her to pay. Also, how would I politely state to guests that this is their responsiblilty when booking one of the rooms? Help me please.