After about a month of this, Emma decides to leave the lawn early- she's finished her letter to her parents, and wants to drop it at the Owlery- so Jenny is left to her own devices. Bored, she examines the forest. It's only supposed to be unsafe at night, right? It won't hurt to go wander around a little in search of unicorns. She won't go very far.
And if she's lucky- unicorns.
Half an hour later, Jenny is deeply regretting her idea. She is completely lost, and the forest has gotten much darker and gloomier. She would go back, if she had any idea where to go. She's taken to making little piles of rocks, to attempt to mark her way; unfortunately, so far all this has told her is that she is definitely going in a circle.
The next time she re-encounters a pile, she branches out to the left instead. She's pretty sure she came from that direction, so maybe-
Jenny is friends with Miranda. Miranda has been compulsively researching Dementors all year; she knows what it means, this cold, the screaming terror. But it's so much worse than anything ever, ever said it would be. She's frozen to the spot, unable to move, brain screaming in terror.
And then the Dementor appears. Slowly but visibly, it approaches her. Is it bigger than the books said they should be? She thinks it is. It's already looming and it's not even close.
Frantically, crazy with fear, Jenny does the only thing she can think of- she shifts away her mouth.
The Dementor stops, seeming to hover in place. Jenny stays frozen in place. The Dementor doesn't seem to be planning to Kiss her... but it's not moving, either, and she's still stuck.
Oh, God. Now what?
"Anyone who's passed their- drat, what's the test name here- O.W.L.s should be more than competent enough. After that, it would depend on who has free time, I'm sure."
"Okay. I'll ask some older Ravenclaws maybe."
"Sensible of you," she approves.
"Is that all, Professor?"
"That's all, Miss Swan. At least until class, of course."
Off she goes.