She's pushing the fuss of her shield under Sigurd's arm. Both steeled items were very close, she took advantage of the amount of time it'd take Sigurd to raise and lower his sword in to another slash to block his second attack at the base, his arm. She's shorter than him, making it easier for her to glue her shield to his right arm, or wedge it in to his armpit. The angle of her shield would begin diagonally, pushing his arm away, and eventually become horizontal over her head as she ducked and continued her spear-sweep - Which would've taken roughly 3 posts to land... by now. Which I'd assume gives Sigurd no time to defend against it.