well that isn't Mindfang; that's Vriska "cosplaying" Mindfang or reaching full tier where she syncs powers with her ancestor.
This is Mindfang
Little different (since she wears pants and not a skirt and a hat unlike Vriska. and her boots aren't red but more brown or black)
And for fabric I believe its all your choice but I don't really recommend silk for this particular cosplay.
Silk is one; way to shinny for my liking (I never use it unless its high quality bridal satin)
And plus it would be hard to either hand paint all those designs or even sew since it moves around alot you could use it for lining the inside of the jacket which would look nice!
I also like what my friend did for her Mindfang cosplay. She used a patterend fabric (I dont know the name of the fabric type D= )
But it came out really nice!
Just some ideas xD