why did the aunt feel sorry on coming downstairs

Dear Student, 
The answer to your question is as follows:
Vera's aunt, Mrs. Sappleton was sorry when she came downstairs because she had been late in receiving Mr. Nuttel and wasnt there before. Vera ad been giving him company. So she was sorry as she made him wait before she could come to see him as it is not a good gesture on a host's part.

Regards