It's because her left foot isn't staying in place the entire time she'd be getting up. He probably would able to step a bit closer before she fully arisen, however her dodge is a 'spring' maneuver, she's propelling her left leg, and abusing the momentum of her arm being thrust aside to help relocate.

I was actually expecting Sigurd's attack! Like, almost exactly how you wrote it. With an exception: I figured he'd attempt to bat away Hyperion before lunging forwards, rather than playing footsies. That would've probably been a lot more dangerous for me & Iolanthe, but I have a trick up my sleeve, still.

I misread 'without any upsets' as if his attack landed without any upsets. Still, Sigurd is trying to outspeed someone with superior leg speed, I'll mention upsets.

Oh, you think I'm forgetting the weight of my character's gear? Nawwhh. 30 pounds isn't even very much, do you even lift? She's barely adjusting the spear in that last post, and the weight of relocating her shield? Well let's say Sigurd helped her make that swing.