I think i've got it!
....maybe.
She is a pilot for a flying exoskeleton using a railgun to shoot thunder. Thunderbird.
A few thematic problems have been solved.
-Removed witch
-Removed harpy
-Hair is visible
-Weapon is congruent with the lightning element
Your last idea work very well too.
It's nice that you don't hesitate to completely change the design if you don't feel it !
Looking forward to seeing the development of the new design
At sea.
Kate is holding a bottle of coke in her hand, leaning over the rail in the backside a yacht.
She is lost staring at the foamy ripples emerging from it.
Her purple dress flappping in the wind a little too much for her liking.
Rick walks onto deck, with a paranoid look on his face.
He walks to Kate in hasty footsteps clacking the wood floor panels.
She turns around to face him.
She observes his face.
K. concerned?
R. We're halfway through. Still nothing?
She shakes her head.
R. If it's taking them this long...i swear they must be up to something.
K. Relax, we've got you covered.
R. Covered?
He leans closer. Cold sweat running down his face.
R. You have... how many was it again?
2 MEN!
And where the fuck are they? dead already?
She pushes him away.
K. They're not dead, they're looking out for your sorry ass. Besides they don't do combat.
R. You have to be fucking with me. What the fuck are they doing then?
K. Support.
He looks around and wipes the sweat of his fucking face, trying not to burst.
R. Support?
K. Yeah....SUPPORT.
Radio hanging off Kates waistbelt beeps.
rad. Kate, come in.
K. yeah?
rad. 3 enemies approaching from 3 o'clock. Estimated speeds around 90 km/h
R. It's them?
K. Probably.
She gets off the rail and walks towards a module planted on deck with a label "Thunderbird" She opens it up revealing assebly parts, arranged for mount.
And starts taking her dress off, hesitates and looks back at Rick as he stands there watching.
K. It's gonna cost you extra if youre gonna keep standing there.
He raises his hands and goes inside.
She undresses and mounts the assembly wich starts dressing her with the EXO.
rad. Kate, come in.
K. Kate.
rad. Object below the watersurface spotted. Moving rapidly
Kate's brows tighten.
K. Torpedo?
rad. Positive. Approaching from 2.07, Z. -40m
Rick comes rushing out.
R. Torpedo???
K. Yes sir.
R. Can you stop it?
K. Negative. Torpedos travel underwater.
R. You have to get me off this boat then.
She looks him in the eye.
K. Negative.
He is stricken with shock and anger.
rad. Incoming. Enemy A breaking Range barrier in 30
K. Charlie, report enemy position on entry.
She faces Rick.
K. Now you listen to me sir, this is what we call a triple bind.
If you stay in this boat and i go to disable the torpedo, they will approach and kill you.
If i go and try fighting them off, torpedo blows this boat up with you in it.
If i try carry you and fly off they will catch up and kill us. Why? because i don't have the means to protect you from a 600 km/h flightspeed. Wich is the only way we would escape to back where we came from. And if we actually did that, do you know what's waiting for us on the beach?
R. What do we do then?
rad. Enemy entering range in 14.
Kate loads her railgun with a rod.
R. you might wanna step back from this one.
rad. entry in....
3
2
1
BOOM! Rod fired.
...
rad. enemy A down. Enemies closing in on subject, 40 kilometers. Torpedo, 35 kilometers.
R. i know. Get me off, throw me in the water, umm away from the blast.
K. It's a torpedo, the sub-surface shockwave will kill you.
Rick sways in silent panic.
rad. Ready for round 2?
K. Loaded and ready. Flight data please.
BOOM! rod fired.
...
rad. 2 enemies still approaching.
K. Fuck.
rad. inbound 15 kilometers.
R. Call down one of your friends.
K. No.
R. I'm paying you $700 000 to keep me alive. Bring down one of your friends. And he can fly me to shore while you stall them.
K. No, that's not an option. I won't risk their safety. it's in their contract. Deal with it.
R. If i don't survive, you don't get paid.
K. Then have some faith in us, or pay more.
Rick is visibly irritated, to the amusement of kate.
R. So what are we doing now?
Kate turns on her boosters.
K. Chill the fuck out, don't you know who i am?
Im the fucking Thunderbird.
The development this character is going through is pretty crazy. I did like the original design but I agree with many of your points in that it didn't really fit the lightning theme of the character. I think the mech suit kinda thing definitely does, and I think you could really play with the exaggeration in the size of those fins and boosters too. But either way it's been enjoyable thus far seeing where the character has come from and where they're ending up. Excited for more!
Did you just wrote a whole chapter?!!! wow!
Really great work! The hardest part with this is to make it not look like too much like Pharah from overwatch o:
Recieved some critiue about the generic face/hair, not matching the written character.
Now fixed.
This is probably the final concept.
I'll worry about the details when i start painting.
Hell yea!
A scenario popped up in my head so i went ahead and wrote it lol.
Now i have very clear images about the setting for the final painting.
It's always more fun to whole-ass something you really like,
instead of half-assing something you "kinda" like.
I totally understand that! Always more fun this way!
I do the same, my entry is based on my own personal project's universe, and this way it force myself to not half ass the work so it's worthy enough to be kept in the book! 
It's a great motivation 
Edit : Almost forgot, great update the face is awesome!
If you struggle painting details, having lots of ref and doing a bit of research into how mechanisms like these work will only benefit you, like moodboards have lots of ref and inspiration and they help to further the piece along
I like the scene a lot. I can see it in my head as an RPG, or an action game with the little text boxes popping up.
These are cool!! I like the last one! The first is really powerful too but we don't see that much of her because of the pose, could work as a bonus illustration 
I looove that first one, so much gesture and movement, the last one is cool too but seems a lot "safer" in approach
Increased motion and flow.
Daamn this is looking nice good work!
