I am not sure we we can lay Drycha's characterization at the feet of GW having an agenda, the Asrai in general were made worse and worse in later edition in a way that feels biased as hell, but Drycha was always shown as having been Fallen, she is the worst of their policy and the representative of their darker impulses, nature wounded yes, but also lashing out in bloody rage and endless spite. Those are the kinds of themes you find all over the sort of fantasy that inspired the setting, including the Lord of the Rings (the Old Forest and the 'black hearted hurons' of Fangorn).