From what I watched of her, her defense improved. I think that video was early last year & I saw her later in the year at the YOG. The problem with her defense I feel is not that she's not quick enough, but she has a tendency to want to hit too good a shot out of a ball she should just loop it back or slice. Either that, or just like what's in the video she just dosn't know how to "push" a ball back.
Quite the exact opposite of her opponent Kremen who beat her in the first round of the YOG who is an excellent defender but can hardly attack.