Hm this is tough. You can’t tell someone how to feel. I know how hard it is when you see someone you care about not feeling what you think they deserve to feel. I’m sure you’ve already told her she’s gorgeous, and has nothing to worry about and all that. I would say tell her that you see guys checking her out all the time on the street. Even if it’s not entirely true, it will boost her confidence. But really, confidence ultimately has to come from her. We are all responsible for our own feelings and reactions to situations. But if you just love on her body, she will probably love on it too. Also, take things slowly. Give her as much time and as much foreplay as she needs to not think about anything else but how good it feels. And finally, tell her how happy you are and how lucky you feel that you get to see her in that way; that her connecting with you through sex is all you need but it’s a huge bonus that she’s attractive on top of it.