What model is this?

That is a reaper bones miniature of a dryad. It’s the spitting image of some book art for the creature from dungeons and dragons. Its not GW at all. Bones are some good cheap models, but if they warp they tend to look horrible. Good luck straightening that dagger.

That's not games workshop, but that would be a perfect branchwrath if you're a slyvaneth player

I recently bought a collection of sylvaneth, but cannot identify this model, any ideas?

Branchwraith.