You: "you could be a model"
Her: "Nah I'm not that pretty"
You: "Actually yeah you're right, you're not"
Say it in a cheeky funny way and you should get a reaction out of her unless she's emotionally numb to the world. Basically whenever a girl says something negative about her appearance she's fishing for a compliment, if you just give her one every time this happens you'll end up looking like a pussy. I usually just say something like what I've written above, but you have to pick your spots and make sure it's not an issue that is overly sensitive to her. Plus if she's an emotional wreck of a girl with no confidence it may not work as well, but who wants a girl like that anyway?
