Creepy, with some very strong moments – the first paragraph particularly. Make sure you capitalise after ellipses, and think about appropriate punctuation, for example “I hate you.” automatically reads more powerfully as “I hate you!”… Also, although you might not tell the reader, know in your mind what the thing in the mirror really is – referring to it as a human being doesn’t quite capture what I think you’re getting at… A grisly and great ending here – a bit of a polish and this is a cracking bit of horror, reminds me of the film ‘Mirrors’… Ironically. MH :)
Ah, multiple personality disorder: always a nice characteristic for some suspense. This is very reminiscent of the Niki Sanders character on Heroes. Nicely done!