Say, "Hey, you're pretty." Then she'll say, "OMG, thank you so much," or something cringe. Then you say, "Pretty f***ing ugly, aha, gottie!"
Backhanded Compliment
Explanation
Explain Bear
Listen up, buttercup. The joke is that you start by giving someone a compliment to get them to feel good. Once they're all happy and flattered, you hit them with an insult. You are not very smart if you think this is funny.