Lorraine's mother is deeply misandrist, which simply means that she hates men. For many years now, Lorraine has been taught to fear, hate, and despise men. The reason for this lies in the circumstances of Mrs. Jensen's painful breakup with her husband, which was caused by his infidelities. To make matters worse, Lorraine's dad infected Mrs. Jensen with an STD, which she started to develop during her pregnancy with Lorraine. So not only did Lorraine's dad cheat on his wife, he also endangered her health and that of her unborn child.
Although Mrs. Jensen never talks about her ex-husband, she's become positively fixated on how awful men are in general. She's developed an obsession with hating men that has taken over her entire life, making it impossible for her to find any happiness or inner peace.
Unsurprisingly, this attitude makes life hard for Lorraine. As Mrs. Jensen believes that boys are only out for one thing, she effectively keeps Lorraine under lock and key so that she won't meet anyone. She has a pathological fear that Lorraine will be raped, which makes her hypersensitive about Lorraine wearing short skirts, walking alone, or riding in cars with boys. Mrs. Jensen's message to her daughter is a simple one: "Beware of men." She constantly dins that message into her daughter's head at every available opportunity.