ah, good point
pastry 
I actually can't see it close enough to know if it's brocade or not. Maybe you guys could tell me...
Since she's using polyester, I was thinking the skirt could have been done like this:
the fabric is put under metal sheets that have an embossed design on it (think giant metal stamps). It is pressed together with heat to make it permanent.
Some students I know have done a similar technique, where they use heat and liquid to create permanent wrinkles on a fabric's surface. This is a Japanese technique... I read it used to be done on silk in the olden days, but if you want the wrinkles permanent, you need to use something synthetic like polyester.
Brocade is made by a different way. It's done by weaving, like you said. I've never made it myself, but I think it's weaving thick and thin threads together. Also, threads can be laid on top of these base threads--it's like embroidery in a way, except the threads are woven in the fabric instead of stitched.
So, if the skirt's fabric looks like it's been pressed someway, then it must have been done this first way. If you can tell there are more threads on top (where the embossed designs are), then it is brocade.
Is it something bad if it's synthetic fabric? I guess for the price, you could expect silk, although you can also get very high-quality synthetic materials.