Below her is a vast forest deep into Spring, an ocean of green below her. Far in the distance, she could make out an improbably beautiful castle, surrounded by a thin mist.

Well, the place she came from is currently, as usual, experiencing autumn, so she's definitely not in her forest any more.

Castle is bad news! She will fly directly away from the castle.

As she flys away from the castle, the world seems to get darker, much faster than it should, almost as if her motion is causing the sun to go down. The trees below her begin to grow taller, and begin to warp, as if somehow leaning into her pareidolia. 

In that direction, there is another castle. This one looks explicitly evil.

Fast nightfalls aren't unheard of where she's from, but she isn't where she's from. ...if she turns around and flies to the left does that affect the astronomical situation and/or immediately present her with another castle?

Time seems to behave normally as she turns off of the line between the two castles, though the forest continues its air of vague menace. She can make out settlements now, cunningly worked into the landscape, houses and other buildings hidden in the lines of trees and the curves of hills. There are people, too, figures moving too and fro through the nearest village. A few look up as she flies by. There are no vehicles, or sign of electric infrastructure, but they don't seem particularly alarmed by her flight.

...okay, those look like mortals, which is what one would expect after having flown through a tear... she didn't expect them to be so calm about a fairy fluttering along overhead but she's not complaining about that. She wouldn't know to even look for vehicles or electricity and mostly the houses look odd for being sized for humans.

She would like to find a nice little stand of trees that isn't right on top of any settlements in which she can land and regroup. She can't eat anything here safely and that's going to make it hard to fly if she overdoes it.

The forest here is dense, but it does thin out a bit towards the white castle on the hill. After a few minutes in that direction she finds a landing site, sheltered enough to not leave her exposed, but where the trees are spread out enough to permit her to navigate the lower level of the forest safely. The sky seems to brighten as she moves back the way she came, and the trees look a little less like they're trying to appear overtly evil. 

If she inches gingerly towards Castle The First does the daycycle and/or plant evilness change in response?

Nothing changes at first, or rather, the change is too gradual to be obvious. But now that she's paying attention, the position of the sun in the sky changes as she moves towards Castle The First. The distance between the two castles isn't small; she's come further than she thought since she started.

The trees seem unchanged by whatever is effecting the time of the day; it just looks like someone made sure to plant thematically appropriate trees nearer to the evil-presenting castle. 

Okay. She wants to set up a little shelter for herself; she doesn't have her own tree, here, but she can construct something that'll keep the wind off, more or less, and make her non-obvious to passersby.

It's not hard to find somewhere to rest. The grove of trees are set into a hill, one side of which has been eroded by a creek, the water carving into the landscape and revealing a soft red dirt. The result is a little rocky area, overhung by ground supported by the tight roots of the 60% evil trees, that will likely collapse well before it could ever be called a cave. But it is sheltered, cool, and pleasantly dry. Far off, she hears something that sounds like a hunting horn, but its distant, and even if someone were to pass nearby, she is nearly invisible here. 

Well, nearly invisible isn't as good as actually invisible, but sorcery doesn't work in the mortal world. The significance of the horn is lost on her, but she'll park in the cave and listen further.

There is silence for a time, then, from the direction of the horn, but closer, she can hear shouts--men and women making their voice carry across the landscape. On the wind there are jingles of bridles. Far upstream of her, a distant figure sprints through the brook's channel, feet moving with unerring sureness over the wet rocks. It's unlikely they'll see her, even passing by, since hanging moss obscures most of the opening to her pseudo-cave. Besides, they seem like they're in a hurry.

Is the fleeing individual a mortal or a fairy or some other thing?

No wings, so probably not fairy. But the figure's speed and grace make it unlikely it's just a mortal, unless mortals are built very differently here. The figure continues to approach as another distant horn sounds.

Well, maybe mortals come in various formats, she hasn't met lots. She holds quite still.

The fleeing figure (something about how he is moving suggests flight more than anything else) is soon within view. His shirt is torn, revealing long stretches of pale white skin, muscles underneath. He is strikingly beautiful, with the sort of face and body poets might go on about. Long black hair frames a perfect face with violet eyes just colorful enough to be interesting without being too off-putting. His ears round to slight points. Despite his speed, he shows little sign of exertion as he nears her hiding spot, but there is a wild desperation about him. 

...about how fast is he going. Say, more or less than seventy miles per hour.

A quick glance between the young man and a few landmarks makes her think he's running closer to thirty. Maybe mortals can just run that fast?

Maybe, how would she know? But the important thing is that she can fly faster than that, and can catch up to him, if she decides she wants to.

The man blows by her, the rags of his clothes whipping about him to reveal an equally muscled back, criss-crossed with scars, and in another minute he is gone. There is quiet for a long few minutes, then a group of hounds bursts from the underbrush, moving with deadly efficiency down the path the runner had taken. Behind them, two more figures on horseback, armed with bows, clear the banks of the river in a jump. They splash into the stream, pausing for a second. One gestures at the other, who charges off on a course parallel to the modest brook , while the first rider turns his steed and begins to follow the water.

Oh wow, animals, those are new and she does not like them at all actually. And she'll be a little cornered, if they discover her here and take exception; there's enough of them to surround. She doesn't want to burn all her recently-fed-ness on flight if she doesn't have to but she might have to.

Promise dithers for a second, and then rockets out of her cave and up above the 60% Evil trees, heading mostly in the same direction as the fleeing fellow such that she can get eyes on him promptly if she decides she needs them but bearing slightly toward the Marginally Less Concerning Castle.