Whoever she trained accomplished their missions perfectly.
Red Flame's intelligence network was very powerful. They received the news live as it happened and they also asked her for mission training.
She did not accept it.
The Shadow League was not as skillful as Red Flame at that time, so facing Red Flame head on would not have been wise. If she went after Red Flame, it would be equivalent of crossing the Rubicon.
Red Flame knew how to play. After she rejected them, they did not say anything and on the surface they seemed to have given up. Yet deep down, they set up traps for her to fall into.
Someone posted a billion dollar reward for a mission and asked her to get rid of a person. She checked it out with the Shadow League's intelligence network and made sure there was nothing wrong before accepting the offer.
Yet, it turned out to be a setup.