Besides, while he knew how he loved her, he had no knowledge whatsoever that she loved him.

She always seemed extremely glad to see him; but that might be explained in different ways.

It might be that what was in her heart for him was really a sort of "old home week" feeling; that to her it was a relief to see any one who spoke her own language, who did not need to have it explained when she was jesting, and who did not think when she was speaking in perfectly satisfactory phrases that she must be talking slang.
The Ambassador and his wife had been very kind to Endicott, and, as a friend of Helen's, had asked him often to dinner and had sent him cards for dances at which Helen was to be one of the belles and beauties.

And Helen herself had been most kind, and had taken early morning walks with him in Hyde Park and through the National Galleries; and they had fed buns to the bears in the Zoo, and in doing so had laughed heartily.

They thought it was because the bears were so ridiculous that they laughed.
Later they appreciated that the reason they were happy was because they were together.