/cgl/ - Cosplay & EGL

cgl could you offer me some advice?
Basically I'm a shit tier sewer and my boyfriends grandma has been helping me make my cosplay which was really nice of her. I really respect that she's helped me and everything, but basically whats happened is this:

>Be me
>Making world is mine Miku dress (inb4 basic bitch cosplay, I mentioned above I'm shit tier sewer and don't do it to be popular it's literally just for a con and I really like the outfit)
>Buys pattern that will suit
>Pattern is for a top so will need to elongate skirt part
>Take the pattern to his grandma
>Bfs grandma cuts the dress pattern whilst i'm not there and the skirt part which needed to be elongated
>Skirt pattern is too thin, not enough poof, not even enough room for a petti
>Feel like absolute bitch r/n for wanting to take it back to her to see if we can make the skirt part more poofy

What can I do to amend the skirt issue? The top part looks fine and all I need to do is sew the black crosses on by hand.
I still have lots of fabric left too so that isn't an issue

Pic related