Did you measure the amounts exactly? Sifting or not should not effect the texture. I made it once and it did that too. Only thing I can think of that made it that way is the weather. I've made it since and its been perfect. Sorry...
Did you put a center dowel? Even so...you told her to put it on the floor. I would not give a refund based on that. HER choice not to follow directions.
I wonder if it can be done ahead by a attaching it to a round gumpaste circle then add the ribbons...let dry then attach to a cake? hummmm may have to experiment on this.