Wear what you want to wear and ignore your daughter. To my son's wedding, as mother of the groom, wore a silk suit that I had worn twice before, once for my graduation ceremony and once to a wedding, I looked for something else, but could not find anything I liked.
I jazzed it up with some braid and got a new slip top, shoes and bag. I also did not wear a hat but had some flowers in my hair.
I cleared this with DDil and her mother, but only as a courtesy.
Buying a garment for one wear only is an environmental crime.
I have just had an idea, why not hire a dress for the day. There are companies around who hire out bridal wear, and that includes mother/grandmother of the btide outfits. Why not hire an outfit and then hire it back.
Members f the Royal family wear their outfits again and again for different events.princess Anne keeps resurrecting outfita she wore decades ago. If it is good enough for them, it should be good enough for your daughter!!!