Trivia: Even though Mary Beth Hurt and Glenn Close played women from different generations, in reality they are only a year apart in age.
Trivia: The man who plays the part of the wrestling referee is John Irving. He wrote the book on which the movie is based.
Trivia: This was Glen Close's first movie (not counting TV work).
Trivia: Glenn Close plays Robin Williams' mother in the movie, even though in real life she's only four years older than him.
Answer: The book makes it pretty obvious that there are a number of factors: 1) She caught Garp and her sister in the middle of things. 2) Garp hurt her dog. 3) She actually hated him from the start and it just got worse.