She manages to move her arm, saving the shield, but leaving herself wide open to the flame blast. Blinded, she still reacts, moving faster than most people think.
T'Challa is as resourceful as the stories she heard about him in her youth. She'd always wondered how the Sentinels had killed him. Now she needs to figure out how to do it, or at least slow him down.
Sarah rockets straight up, impacing the celing, and trying to bring as much of it down as possible. Sure, it'll make a lot of noise, but she hasn't been subtle in the first place. And she figures if there's enough rubble falling, he can't dodge all of it.