I understand your confussion, because she doesn't tell you all the truth in order to don't panic you.
Also, to be honest she is kind of the three things. Witch, Succubus and somekind of Demon's daughter. But neither of them actually.
It's a witch because in those times any woman who did something weird was considered a witch and also because they are from one of the lands where withcery was more popular.
She is a succubus because that's how sexual vampires are known, those who take your life through sex.
And Satan's daughter, well, daddy issues I guess. xD