Spoilers alert
Watching this currently for the millionth time and as much as I understand Jenny was a very troubled character with a horrific childhood, she's bloody mean to Forrest. Constantly dipping in and out of his life, using him and never telling him when she had his child. I never understood that. What kept her from being honest with him that he was a dad? He was a good guy who truly loved her and he had a right to know he had a son. She only got in touch when she was ill and needed help.