"You know that I see you, right?"
Twilight was sitting at her desk, writing in her diary. She closed her mouth and wrote a few additional words on the paper, then opened her mouth again.
"I don't know what you hoped to learn about me by sneaking into my bedroom, but I don't think you will learn anything useful. Diaries are not exactly known for holding national secrets..." she said and paused, reflecting. "... okay, that is not strictly true, there ARE some people who are irresponsible enough to put such sensitive data into their personal journals, but I am not one of them."
Twilight spend another minute in silence as she added a few more lines. When no response came, she put down her quill and turned around, facing the unassuming fern sitting in the corner of her room.
Then she waited a little more.
Then she coughed. "... so, uh... you can transform into yourself, Chrysalis. And you should know that this room is screened against teleportation, so yeah... that exit won't work for you. I also don't feel any potent magic emanating from you, so I'm guessing you didn't get to absorb any meaningful amount of love to put up much of a fight..."
Twilight waited a bit more. The fern still did not move. Twilight sighed. "Oh, come on! This fern was not here ten minutes ago! You're also not a surprise present from Starlight because she always without fail adds a note in the ledger regarding any and every purchase of goods that are given to me or to the school, even if she pays it out of her personal fund! So stop playing around, Chrysalis!"
Twilight stood up and prodded the plant with a hoof, imagining herself jabbing Chrysalis forcefully on the chest. "The jig is up, so QUIT IT!" she yelled.
Continued lack of response provoked a growl from Twilight. She aimed her hoof lower and almost punched the pot that was housing the plant. It made a loud 'CLONK!' sound, tipped over, and landed a moment later with a quieter 'clunk'.
...and the contents of the pot spilled out. A small patch of dirt covered a portion of Twilight's bedroom's floor.
Twilight paused.
"The potted plant... separated into three," Twilight whispered to herself, forgetting to turn on her Inner Monologue when she was no longer addressing anypony in particular. "The dirt and the plant and the pot are all separate now... if it was Chrysalis, then she would turn again into changeling, with her guts spilled out. But it didn't."
Twilight took another minute trying to agree the things she could see with the things she knew, and another thing has dawned on her. "Wait," she said, putting a hoof to her face, "A changeling can't change their mass very much. Why was my first thought 'Chrysalis' when I noticed this fern? I should have remembered that. I am better than this..."
She put the dirt and the plant back into the pot. Nothing was broken, so there was not even a need for a measly mending spell. Twilight then has put her diary into a specific spot in the giant bookshelf covering one full wall of her bedroom, making sure it blended in with other deliberately-boring and similarly-colored titles.
Then Twilight left the room. "Maybe Trixie will know something about this. Her ledger-discipline is a lot worse than Starlight's..."
A long moment has passed.
Once it was absolutely sure that it was safe to do so, Twilight's writing desk loudly sighed in relief.