About to Lose It

My fmil offered to make the flower girl dresses for our wedding shortly after we got engaged. She was basically using it as an excuse to travel to North Carolina to see her grandchildren (the flower girls, ring bearer, and usher). I said from day 1 that the dresses needed to be done 1 month prior to the wedding so I could purchase matching flower girl baskets, shoes, and headbands for the girls to wear. Our wedding is 1 month from this Thursday and the dresses still aren't done. She left for Ohio today to take some of her belongs to her other son's house. She is moving in with my fiance's brother. She will not be home until late Wednesday night and works Thursday so there is pretty much no way they are going to be done by the deadline I gave. My fiance keeps defending her even though she keeps giving us excuses. She will tell us they are going to be done by x date, but then she has things suddenly come up. Last week she told me they were going to be done by today or tomorrow, but surprise surprise they aren't done. I want to just buy dresses from either Amazon or Walmart which is what I planned on doing from the very beginning, but she insisted on making them. I am afraid this will cause a huge fight between my fiance and I, but I don't want to not have dresses for the girls to wear. Originally, she was going to mail the dresses to them, but if they aren't done that is rather difficult to do. Would you recommend giving her more time and hope she actually comes through or would you buy dresses?