To the above comments: it's highly unlikely that she's retarded.
Milestones for 2 to 3 year olds suggest that they should be able to put together 2 word sentences (she made a passable 4 word sentence) and they should almost be able to go up and down stairs (at the very least, in the video, she can stand).
She can also hold a pen/stylus in the "correct way" (a 3 to 4 year old milestone) and draw a scribble well (1 and a 1/2 year old milestone).