As Twilight fled through the streets, she realized that running would not be an effective tactic against Rainbow Dash. The blue pegasus was faster, stronger, and had more endurance that Twilight - any physical competition was doomed to failure.
Having determined this, she turned around a corner and teleported inside a house next to her. With a sigh of relief, she dropped to her knees as she caught her breath. Rainbow Dash flew right past the building, oblivious.
A young filly screamed, shattering the fragile silence. Twilight turned, seeing the filly, a light blue pony with a lavender mane and a horseshoe cutie mark. Quickly, she covered the filly's mouth to stop her from giving away Twilight's location, but it was too late. Even as a parent ran into the room, there was a crash as Rainbow Dash broke down the door.
"Get your hooves off that filly, Twilight!" Rainbow Dash yelled. "Trying to take hostages won't do you any good!"
Twilight panicked, quickly teleporting back out of the building into the alley she had been in before. Back inside, the filly bolted for cover as Rainbow Dash looked around. It was only a moment before the blue pegasus was back outside again, but by then Twilight had made good on her escape.
Twilight's mind was blank. All she could think of was running. Getting away from Rainbow Dash. Hiding. Where could she hide?
Sweet Apple Acres. The apple trees' foliage would make seeing her difficult from the air, and their nearness to each other would make it harder for Rainbow Dash to fly between them if Twilight was discovered. After several minutes of sneaking through Ponyville, she finally got there, sitting under an apple tree to catch her breath after her flight.
"You might as well give up, demon creature! You will not escape again!" Applejack's voice rang out in the still air.
Twilight had underestimated Rainbow Dash. It was understandable, given her state of mind, but it was her undoing. The pegasus must have known she wouldn't be able to find Twilight on her own, so she'd come to ask for Applejack's help. Twilight had walked straight into discovery by Applejack.
On the other hoof, this was Twilight's one chance to get Applejack on her side. If she could explain what was going on to the farmer, Applejack would surely help her.
"It's not what you think, Applejack! I'm not a monster, I'm Twilight!"
The farmer's response was cold. "I don't care who you claim to be. Rainbow Dash told me you attacked a filly, and that's all I need to hear in order to know that you're bad news!"
"It's not like that! I can explain!" Twilight was frantic, now.
Applejack's voice didn't get any warmer. "There's nothing to explain. I know everything I need to already."
It was futile, the unicorn realized. The earth pony had made up her mind, and her stubborn nature was legendary throughout Ponyville. Twilight turned to run, but a rope caught around her trailing hoof and she promptly fell flat on her stomach.
Applejack laughed. "Did you really think I'd let you get away so easily? You won't get away from me like you did Rainbow Dash. There are no little fillies to use as hostages here."
Twilight flinched at the hate in that voice, but there was nothing she could do. Her chance to win over Applejack had already been lost, it seemed. Calling on her magic once again, she burned through the rope and leapt to her feet.
Fleeing Applejack was as futile as running from Rainbow Dash, but the same tactics wouldn't work here. There were no buildings to teleport in or out of, the trunks of the trees were too narrow to use as cover, and though she might be able to teleport into a tree, she'd disturb the leaves by doing so, revealing her location. Desperate, Twilight fell back on her earliest magical efforts, the very first spell she ever learned.
When a unicorn horn charges with magic, part of that magic is expended as an involuntary side effect that produces light; this is why unicorns' horns glow when they are preparing to cast a spell. There is one spell, thus, that any unicorn can cast. Even young unicorns know it. Light.
Applejack flinched back, blinded. Shaking her head, she squinted as her vision slowly returned. The monster was far out of range now, beyond Applejack's ability to catch up to her.
Twilight galloped away. Away from Ponyville, and the maddened ponies therein. Against such madness, she headed for the only place they still would not dare to follow. She would head for the old Palace of the Royal Pony Sisters, deep in the Everfree Forest, where the Elements of Harmony had defeated Nightmare Moon. There, she would be safe.
There were still intact portions of the old palace, after all, and the ancient wards still held strong, even after a thousand years of neglect. The magic of the princesses tended to produce permanent effects. The more dangerous inhabitants of the forest would still avoid the place, and the nearby foliage should be safe to eat as long as she was careful.
It occurred to her that Princess Celestia should be told what was going on, but Twilight had no means of contacting her mentor without Spike, who would no doubt be being guarded by her friends in case she returned. Then again, the princess would find out about it soon enough when she came to retrieve the Element of Magic, so it wasn't that much of a problem after all.
Twilight had escaped Ponyville, and had a safe destination in mind. She could hole up there until she found a way to return to her normal self, and then return.