He had been visiting Isabella and her family immediately before his return to the area.
I assume he arrived late in the evening.
I assume that Isabella lives in Brunswick Square, where everything related to their home and family is fine.
Mr. Woodhouse wishes Isabella still was with them, and assumes that Isabella wishes the same thing, therefore "poor Isabella" (who is in fact quite happy in her marriage and children) must be suffering because she is not with them.
Student or Learner