For the light in the background, I think so too. I will also try a few different ways to position the lightnings in the back ground maybe.
About the thickness of the lightning I initially liked it this way. I wanted it to look more like electric arcs, like, Nariko has all that energy mostly inside of her and I didn't want it to be too "over the top", because I want the whole character to be really, simple/sober, including the way her power looks.
But all of that just to say that the fact is : Yes, in the end, it's too thin 
At least now I have a good base, I'll work on that now.
(But ugh... I really went outside of my comfort zone with this piece : with all these light sources and perspective
)