I think I'm losing my mind

I reread yesterday's post, and I'm not entirely sure what was going on. Was it real life? Was it just fantasy? I didn't know. I shook my head in annoyance with myself, and turned around to find the Creepy Girl sitting in the corner again, painting a mural on my wall. The mural was entirely black, with bright touches of gray here and there.

I approached and said hesitantly, "That's, um...that's my wall..."

"I know. It's a good wall," she nodded resolutely. "Good plasterwork. Did you do this yourself?"

"No, actually I didn't."

"Shame," she said breezily, adding a dab of gray to the mural. I noticed her accent suddenly had an element of faked Brtishness. "Thought you had some talent for once. Plastering walls. It's good work."

"Can you stop trying to be effortlessly casual and realize that this is not normal? What is going on?" I exploded, nearly knocking a tub of paint all over my floor. "What are you painting?"

"A My Little Pony for my little sister, Taylor. She loves My Little Pony, and her birthday's tomorrow. So shut up, bozo, I'm trying to finish this."

I examined it closer, and guessed that it did look like a My Little Pony, if the My Little Pony was hit by a truck, received really bad plastic surgery, and bathed in 1920's movie magic. I shook my head slightly, and asked, "Don't you have walls of your own? So Taylor can see the mural...at your home?"

She gave me that look again, the one where I feel as though I'm the one who's doing something wrong. "You have better plaster. I think, " she smirked, "I told you this. I noticed that the other night."

I had never felt so confused and defeated in my whole life. I turned back toward the door, determined to call the police on this oddball. "Okay. Just...just don't get any on the floor, okay? No paint on the floor. I'm just going to make a phone call."

"Wait!"

I turned around, because all of this was getting the better of my curiosity.

"How did she get in here?"

There was another girl sitting next to the Break-In Creep, and I'm pretty sure she wasn't there before.