You need to increase her ATK value. Ryoko's ATK is saved when you interact with the green orb for the first time. It's necessary that she has 10+ more ATK when you interact with the green orb again later.
I don't think I can get her stronger through weapons my next strongest axe gives +9 attack, and I'm pretty confident I've exhausted all attack ups. I'll keep searching for a way though.
