Once she's cast it on you, you have the spell listed in (I think) illusion. If you select that spell and cast it on anything living, you will see everything with that greenish tint, and much brighter just as you do underground right after she casts it on you. If I cast it on say a dragon that I'm fighting, I get several hours game time of that "night vision" (have a look at my posts in "shoe your screenshots" thread to see how it works when cast on a dragon). To get rid of it I summon something small and short lived... like a rat or skeever, cast Baylna's Spell on the summoned little critter, and when the critter goes away so does Baylna's spell. That way I'm not stuck with it in daylight.