Drank 2 beers with WBS tonight... asked him about this sitch.
His opinion:
Safe. No appeal granted.
His thought:
Runner passed the (safety) base. Assumed to have touched it. Now on white base. In that instance, that is the "return" allowed. She's standing on the base now. She's safe. No appeal allowed.
For those who don't know who WBS is, turn to Pg 198 of the ASA Umpire Edition.