I think it's more of a 'saw cut' motion. The heat from that blade, you can't ignored due to inconvenience.

The pivot indeed reduced how strong her attack would be, and in fact would make it easier for her to sneak its full length under Sigurd's shield, which is covering his left side... and not his lower left side. Also, since she's ducking, her knuckles could very well be dragging across the ground as well, however they weren't, so I didn't mention that.

The main issue here, is that the blade breached Sigurd's guard, that's what I don't see your argument denying. The second stab motion she's making is all the cut she needs to do whatever damage she can from her current position. Be that a mere flesh wound, or a grievous gash, that's up to you... or Drifting Pollen.

If it was a lightsaber, this battle would have already ended.