A few moments later, she raises her free hand and I can see her chest rise and fall once as if she was gathering strength for something. She turns her palm to her opponents, adjusts her footing, and assumes a defensive stance. Then she casts a powerful Shield Charm and holds it in place with her left hand alone, while continuing to block any Expelliarmus that gets out of line with her right wrist. Most of the opposing spells hit her shield, where each of them instantly fizzles out. After about a minute, the shield wears off and Granger immediately summons it again.