Bella came quickly as well, with Rodolphus at her side. She wouldn't have dared appear without her husband. She had, however, given Narcissa a good five minute lead. She knew what her sister must do and she knew that Narcissa must do it alone. But with Rodolphus is was important to Bella that they show as united a front as they ever had. Together they had been the most faithful to Voldemort after his initial demise, she would make him remember that by sheer force of will if it could be done.
Entering the house, Bella knew that Voldemort would know she was there. She paused in the entry way and came in only as far as the living room. There she grabbed her husband's wrist. "You will wait until my sister has finished." Bella had no doubt it would take more than five minutes for Narcissa to work up her courage. We will wait. She made sure to think it clearly enough that Voldemort might incidentally pick it up, even if he wasn't searching for it. She had done her job as he had asked. Narcissa was now completely in his hands without the influence of her husband.