Why did Wanda create the hex?

Later in the memory, after Vision is killed, Wanda drives to Westview where, apparently, Vision had purchased a plot of land where they could build a house and “grow old together.” (Can Vision grow old?) Wanda is so overcome with grief that magic just bursts right out of her and creates the Hex.

Why are Wanda’s fingers black?

if you look at her hands you can see they turn black when she uses the darkhold. her blackened fingers are her price. the reason her fingers are affected is because of how she useed the darkhold energy the most.

Did Wanda intentionally create the hex?

12/12 Wanda Creates The Hex Involuntarily Wanda’s emotions unlock a new power within her, one that creates things from nothing. This chaos magic results from Wanda’s lack of training; she eventually realizes what she has done and regrets it, but the Hex was not an intentional creation.