He said nothing, only handed her a band to put on her wrist. The band was designed to make remembering her features difficult, but not so much that it would arouse suspicion. Aberforth would not have one, as their names would have been recorded immediately upon entering the building anyway. The name of Dumbledore would be recognized anywhere, and he would be the one studied. His presence while Hermione visited her vault was easily explained away: he was her employer. It wasn't uncommon to accompany an employee to a vault to check that the money was exactly where it should be.