I think she certainly did above 400 miles with 410-430 miles being realistic if we assume she is overly exaggerating how much time she actually spent on the treadmill. This could all be easily answered if only Millet Sports would release the YouTube links for the missing videos.
OK. 60 miles/day for seven days. Can you point me to a single piece of evidence that suggests she is capable of that feat? Wouldn't you expect there to be something objective out there in her past considering how she is going all out for attention? If she was anywhere close to being capable of this, there would be records. Strava, Power of 10, official races, et cetera. I have seen nothing to support this claim. Her saying she was on the treadmill for 18 to 20 hours a day is irrelevant. Do you also believe the claims that she lost 28 lbs?