Made this one up in health class today

Suzy gets invited to go to her first high-school party with alcohol. Her mother is no fool and understands how teenagers are, so she sits Suzy down and gives her the talk "Now Suzy. it is normal for girls and boys your age to begin to have sex. It is natural and nothing to be ashamed of , BUT if you do have sex you need to make the boy wear a condom. Now, most boys just despise wearing condoms so you're going to have to be clever to get them to wear one. If the boy doesn't want to wear a condom, tell him you have crabs. If that doesn't convince him to wear one, tell him that you have gonorrhea. If THAT doesn work, tell him you have herpes. If even THAT doesn't work, tell him you have AIDS."
So suzy goes to her party and sure enough her and a cute boy end up in a bedroom fooling around. They're about to have sex and Suzy stops him and tells him to put on a condom. He says its fine they don't need one, so she tells him she has crabs. He tells her he doesn't care lets have sex. So she tells him she has gonerrhea and he says he still doesn't care. Then she tells him she has herpes and he still doesn't care. She finally tells him that she has AIDS and even THAT doesn't stop him and they start banging! When they're finished Suzy says "Wow, you must really really like me if none of that stopped you from wanting me!" and the boy goes "nah, I just already have all those"