Mother Drama

My mother, God love her, has made every big event in my life absolutely miserable. My fiancé and I are getting married, about 2 hours from our home (semi-destunation) in April. We have found a property where we have rented the house and the barn for the venue. We made the decision very early on that we would have friends stay at the house instead of family. My mother, who is in the middle of a divorce, was doing really well at keeping her nose out of the wedding planning, until recently. She originally was pushing me to do what we wanted to do and this is our day so we need to be happy until lately when all of her comments are about how no one is going to make the drive to come, how dare we make it so far away, making me feel guilty for my grandparents having to drive then not allowing them to stay at the house. Now she is grumbling because I made it very clear she wasn't welcome to stay at the house. We also went dress shopping for her for the wedding and me for the shower and then made me feel guilty for making her buy a new dress so I ended up buying her dress for my wedding and my shower. I also might add that we are paying for the whole weekend, except for people's hotel rooms, out of our own pocket. We specifically decided against having a wedding party so we could avoid all the drama and now I'm at witts end with my own mother.. So my question is how do I make her back off, stop nagging, and also tell her very politely that she is not welcome the day of the wedding while I am getting ready? I do not need her breathing down my neck the whole day.