A man's lack of instinct.
Also by studies.
Villain is the answer I believe
Answer:
By sympathizing with the young couple.
Explanation:
The whole story is narrated mainly in third person. There are a few times where the narration shifts into first person but the narrator does not seem to be another character in the story and does not expand his view beyond Della's.
Kelseys reaction to Ryder is (evidence of )her thoughtful and caring personality.
