How can I convince her that her outfit is really nice?

I have had epic dramas getting my mother to choose an outfit for my wedding in November. We had looked in so many places at so many things and none were really satisfactory for her. But yesterday we went to a shop on the advice of my FMIL and she bought an outfit! It took me so long to talk her intp it even though she does like it, she is just indecisive. I told her how flattering and appropriate and lovely etc it is on her so she bought it and seemed happy with it. But now today she is saying she has doubts because the fabric of the skirt crushes easily and she doesn't want to look bad. but I said inbetween the ceremony and reception she can go back to her suite and iron it and it will be all good. but she still has doubts. I think she is worrying too much. I have told her over and over how lovely it is. What can I do to reure her and stop her worrying?