RD, that's fluff for "we don't wanna make up stupid facing rules".
But more to the point, I was referring to checking if one can use Tumble while perfoming a Run action (which is a full-round action, after all). I don't really see why not, I just never saw it used.
Tumble does apply a half-speed penalty, however, so Claudia is only going to get 100 feet away from the zombies (which is just as well, even on a charge they can't cover more than 60 feet).