That Sorilea must be a DF and knows such rarely known weaves. Both is pretty unlikely, considering that Sorilea helps Rand/order very much by keeping the Aiel together (as Aviendha notes in TGS), even suggested to kill Semirhage (which a real DF would certainly never dare), and is only a weak channeler. Also Sorilea's PoV in LoC, ch. 51, didn't indicate that she is a DF, but that she is really concerned about Rand's well-being. I also doubt that there will be another Verin-like revelation, namely that Sorilea is actually a "good DF", or that she was under "positive Compulsion" like Elza.

In my view, BS's answer implies that SH gave Elza this knowledge of several rarely known weaves, when he made her into his tool. If another Forsaken, e.g. Graendal, was involved, Elza wouldn't have been essential for SH, as BS told in another answer.