Nukes blind people. Glassing is a space nuke. Therefore, looking straight into a space nuke would probably at least temporarily blind Kat. Hell, the in-game "eye light adjustment" tech shows this personally--if you're looking right at the beam when New Alexandria gets glassed, almost everything else goes black.
Likewise, on the Pillar of Autumn, if you don't stop the cruiser in time, the beam turns your whole screen white... but you don't actually die until about three or four seconds after.
Also: muscle memory could have a little to do with it when she was temporarily blinded. Augmentations and practically living in your suit would probably have something to do with it.