You should look to see if there might be a familial connection between your Lettie and her landlady. Was the landlady born in the same place as Lettie's mother or father? If so perhaps the landlady might be a cousin of the mother or father. Lettie was a young Catholic girl who went to work at a hotel in the District. If she had such an upbringing her parents would have been very careful about her boarding situation. I bet there are no males boarding in the same household.
Look carefully - trace the landlady back to see if she may have lived in the same places as the mother or father of Lettie. She may be another connection and perhaps a hint as to missing maiden names.