In her impatience to run away, he grabbed her by the arm to stop her. She's terrified that by keeping herself too close to him, she will lose her strength to protect herself. He's counting on that, as he knows what's best for her. He knows he must break that barrier and get inside of her.
He refuses to allow her to leave his side, and instead makes her face him. His physical strength outwits her own, but his demeanor soon turns gentle as he forces her to look at him. Eye contact is her undoing, as she knows she cannot maintain her bearing if she looks fully into the eyes of her future.
A rush of fear crashes over her. She cannot put her heart out there again for it to be broken. She must maintain her self-discipline. She must run away while she can. A life of solitude is preferred if that life is guaranteed no heartbreak or pain.
He is unwilling to allow that to happen. He knows their love is stronger than her fear, and he will fight every demon she has to get the chance to cradle her with comfort. But right now he must show her that it is not acceptable to run from him.