This is a tough one Danes. If you don't plan to have a relationship with her, you have to tell her you can't accept the gift (no matter how much you like it lol). If you kept it, you would be giving her the impression you want what she wants. When you tell her you can't accept her gift, that would be a perfect time to tell her you only want to be friends with her. I hope that helps!!
Stay thirsty my friends.