Mother of the Groom says she is "disappointed" in me 2wks from the big day.

My H2B spoke to his cousin who asked (after saying she couldn't attend 3wks ago) I'd she can come yo the ceremony. I said no as we couldn't amend out seating plans, food orders and everything else this late in planning. Everything is done and I don't want to have to reorganise things. We said no, and said she and her husband are more than welcome to our evening celebration. She qas absolutely fine with this as she knew it was very late of her to ask the question. 5 minutes later my future in mother in law calls and said she is disgusted and "disappointed" with me (not my H2B). She said I was put of line. I am so angry and upset that 2wks to the wedding she is trying to take charge and bully me into doing what she wants. My H2B was supportive pf our decision to say no. But his.motger put the phone down on us. I don't know what to do. She has questioned every decision, every detail of our day and has tried to control every aspect of the wedding. She qont speak to us until we apologise (though we've done nothing wrong) and is tp come out for my hen night. I don't know what to do.
Any advice please? This literally happened 10 minutes ago. Thanks x