Why is Mrs. Jensen contemptuous of men?

In the book, Mrs. Jensen is Lorraine's mother. She's a private nurse and often works the night shift. Her patients are usually elderly and terminally ill. Lorraine and her mother have a difficult relationship, as Mrs. Jensen is a deeply unhappy woman. According to Lorraine, her father left them fifteen years ago when his parents got a legal separation. Since Lorraine's father is now deceased, Lorraine states that the separation between her parents is permanent.
Mrs. Jensen has a great distrust of men due to her husband's actions during their marriage. Accordingly, he had contracted a venereal disease while she was pregnant with Lorraine. She discovered his illness when the doctor called and warned her not to engage in any sexual intimacy with her husband until he was cured. When Mrs. Jensen found out that her husband had actually cheated on her, she filed for a legal separation. According to Lorraine, this is the main reason that her mother is contemptuous of men. Mrs. Jensen equates all men with her faithless husband; she sincerely believes that all men are untrustworthy and that they are only interested in sex.
Because of her hangups about men, Mrs. Jensen is always warning Lorraine about boys. She tells Lorraine not to get into a car with any boy and warns her that men "have dirty minds, and they’re only after one thing." Lorraine imagines that a good psychiatrist would be able to help her mother, but she concludes that her mother's problems are so "deep-rooted she’d need three years of intensive psychoanalysis" just to see some results.