It seems a bit contrived that she's Death personified and the fight club guys just happened to give her a scythe, traditional weapon of the grim reaper aka Death. Maybe you should have her take the scythe with her from the lab when she escapes. That might also explain why they further train her with it when she'd being blackmailed.
She doesn't look particularly like a frail fighter. The nice topstitched coat with all the buttons in place, the rings on her finger, the heavy boots that wouldn't help her move quickly in a fight...if this was a design for a gothic girl in a nice coat this'd be fine, but I'm not getting 'club fighter' from her at all.
A few suggestions:
If you wanted to emphasize her frailness maybe you could make the coat too big?
How would she keep her grip on the scythe but keep her hands protected- Hand wraps, fingerless gloves maybe?
Perhaps cover her neck up? It looks almost vulnerable, both from a fighting and emotional viewpoint.
I think the notches would look more natural on the wooden part of the scythe...it seems like it'd be more easy to carve into at any rate.
Is the ring supposed to be in two parts or does it just look that way? It might look more imposing if it was chunkier- the first time I saw it, I thought it was two fashion rings.
I'd recommend trying some more designs. This is a good start but she could be quite a bit stronger if you pushed the concept a bit.
“If you trust in yourself, and believe in your dreams, and follow your star, you’ll still get beaten by people who spent their time working hard and learning things and weren’t so lazy. Goodbye.” - Terry Pratchett