Skylar

It's definitely the sleazy blonde isn't it?

Her never training could be boiled down to the OG Viola just being such a bamf that when she takes over she naturally does excellent in battle.

But never exercising at all? Being a badass does NOT mean your body will always be able to keep up, actually it's the exact opposite and without maintaining a certain level of fitness your body WILL fail you.
Example: you stumble and know you're falling and that it's going to hurt but aren't fast enough to have caught your balance or put your hands out to break your fall; you eat grass.
They could have done a tiny little scene with her sweating and Zeno giving her a strawberryade all cute-like