I am someones MIL and my thoughts would be " How beautiful that my DIL would take the time, energy, patience and LOVE involved and required to make something so very special.
I would leave it as it is and say nothing to the MIL about the ironing.
My guess is......she wont even notice!
She will more ingrossed in the fact that the quilt is so beautiful and that you took the time to make something 'personal' for her.
Shop products mean nothing to me.
Just as I enjoy getting a handmade greetings card from my children , rather than a shop one.
Crazy but true.