It looks good! I love it when people sew Medusa's jumpsuit as a one piece, instead of actual... two pieces. If you understand what I mean. xD Because her outfit is clearly a jumpsuit, not just a two piece tracksuit. And I can't tell, but I hope you used stretch fabric? Her cosplay looks a lot better in person if you've used a stretch fabric.
All I can tell that is a bit off is that you're missing Medusa's collar. She has a collar that goes around the hood, and it has gromets in it. (Think... like in usual sweaters, the drawstrings. That little hole the strings go through. Except it's in her collar). You can see in her reference pictures you provided xD I think Most people just don't notice it's an actual collar because you can't see the line dividing it from her hood because it's drawn in black. So most of the time, people don't do her collar. The hood comes out between the collar and your neck, if that makes sense.
That's really all I can think of. :] It looks good! I like it.
As for Medusa's wig, I'm not sure what to suggest... the little twist can be done easily. Don't use TWO elastics, don't braid it. Actually make it twist. I've seen people actually braid it. If you twist the two strands of hair and them tie them together at the bottom and just let go, it should twist itself into her 'braid'. Just mess with it from there, and you should be able to find a nice twist that matches hers.