The idea is great, actually, this girl telling this creepy story and forming an emotional connection to this thing, and then boom he's there! But the format (Talk talk talk, bang! end) could use some work, as could the stiff, unnatural, audition monologue style acting.
There was a lot of buildup to the "She killed my...cat" but she didn't really seem horrified, saddened or even much affected by the recollection of this event. Same with seeing her grandmother die. There was just a lot of disconnect between what she was saying and how she was behaving. I would've actually prefered that she was less specific about what slendy did. Like, specify that something bad happened, and that it killed her grandma, but be a little less descriptive about the event would've made it a little creepier for me. Not sure why, and I just mean like a tad less descriptive. Not much.
I liked the bare bones of it, I think with a little experience and learning she could write some genuinely creepy stuff!