Really good all the way up to the end..the kid's bashing her head in talking about them then weird reflection of grandma in the mirror...to me it ended too abruptly with no explanation of what was going on, what did she think was in her head? what did the grandmother look like, or what was she? Needs more information so you know what's going on

The beginning was really hard to stay interested in at first because your rythm was always the same and didn't flow. The sentences were always disected by your descriptions, but then when you came to the dinner part, it changed for a while and I was drawn in because it was more natural feeling.
But then you went back into that awkward rythm at the part where she's talking about the curtains (good descriptions, just needs to be a little easier to follow, more comfortable for a ten year old's language style you know?). But then towards the end it went back to sounding more natural, and a really really well written picture of the sister when she's in the bathroom.
I can tell you were trying for a suspense/thriller type deal here at the end, but I think you just need a tiny bit more explanation to whats going on, there's not enough even, to assume what you maybe are trying to portray.
Overall though, good job!! Keep it up :D