I'm pretty new to drawing faces in Inkscape and in digital art for that matter so this was a huge challenge I can tell you. Lucky for me, I'm rather skilful with the bezier tool, which really helped the situation. I'm not new to shading, so getting the face done in that respect was not too hard but getting the proportion right was difficult, like eyes, mouth and nose. Of course I always use reference images and this was no different.
Inkscape uses real blur, not vector feathering, so it's very hard on the CPU and it's very slow with lots of shading. I had to mostly work in non filter mode because of the blur and I have a Quad-Core CPU, since Inkscape doesn't do any GPU acceleration.
Now, the real pain came when trying to figure out how to do the hair and trust me, it wasn't easy for me to do, since I've never done hair before in vectors. After some playing around, I thought screw it, I'll do the hair locks one by one. So I did a load of bezier curves and put them together into a lock of hair, with some shading over the top, then duplicated them to try and create some randomness.
My vector skills got tested to the max and beyond, thankfully it paid off well.








And for the dreadlocks, you can save a little time using the interpolate sub-paths feature on the path effect editor (ctrl+shift+7).
Anyways, your Neytiri piece is very very beautiful!!