I give her top marks because firstly, her expressions are always controlled.She doesn't go overboard but instead she does it in a very cute way and they're well-timed as well, which enhances the meaning of words she's singing and is engaging to watch.
Secondly, she added her own bit to the song and that's something which impresses me a lot that is being creative rather than being a copycat. Thirdly, the original song was sung by three singers but she managed to sing all the portions all by herself.
Fourthly, it's her unique way of singing that sets her apart form the rest!
So, Bravo to Sara for her rocking performance!