redlemon is wise.
Especially the part about not doing something she
really doesn't want to do. I've even had people under hypnotic influence, pretty deeply, that have resisted the suggestion I was making because they just didn't want to do it.
Out of town is always a good place to bring this up, especially out of state; you're never going to see any of these people again. OR, on the other hand, it might be that she's worried about complete strangers seeing her, and would be more comfortable if it were friends peeping. Talk to her about it in as comfortable a setting as you can, and find out exactly what she feels is strange or wrong about it. There's probably a way not to involve that particular aspect and still have fun.
