>>40501321>>40501462>>40503172>>40503971Jynx is based entirely on the pop-culture image of the Yama-uba. In a popular play she first appears as a horrible woman with golden white hair and a black face (a common depiction for youkai) in a tattered red dress then, in the last act, she transforms into a beautiful woman with blonde hair and a beautiful dress and starts belly-dancing. Yama-uba are said to cause Blizzards when angry and, in the modern era, they help Santa Claus (which is why Jynx do it in the anime). Jynx also learn Sing because the Yama-uba puts a person to sleep in the play and Draining Kiss because being able to drain life-force is a common trait in youkai.
It's not expected for non-Japanese to know this but in the so-called INFORMATION era the least you could do is a bit of research before jumping to conclusions.