I don't think they ever pretended Natalie did all her own dancing, especially the difficult stuff. I doubt any of the audience was fooled either. They even said they choreographed easy dance steps for her.
If Natalie was required to thank everyone who made her look good, she'll also have to thank those in lighting, make-up, costume, workout trainer, dietitian, cameraman, etc.
eta: I also doubt she did one big dance number from beginning to end. She probably did small chunks and they spliced them together. I can believe she's able to do at least 80 percent and not just 5 percent that Sarah Lane has claimed.