Check out the video of the 350 in Monaco. She is not spent at the end. Yes she goes to the track, but that is more fun/elation than fatigue. She did not look that tired at the end.
Yes there was some strain on her face/teeth gritting during the last part of the race. But she did not show the utter exhaustion of the runners behind her at the end. (Many ran PRs or near PRs too). The effort seemed to be more focus/concentration from being near speed maxed out near 60 sec/lap than fatigue.
What is her 400 PR?
Yes setting a WR can overcome lots of fatigue at the end of a race, but she may be able to go faster. She claims to have been focusing on 5000 training.