Holly and Jeff are so in love that when Holly tells Jeff she's pregnant he avoids her and flirts with other girls and when he does finally talk to her it's to urge her to have an abortion so his life isn't ruined.
Holly's mother wants her to get married, and that's what Holly thinks she wants too. Jeff's father wants him to get some of his friends together and claim they slept with her as well so Jeff is off the hook.