I'm sure she'll turn out to be a lovely well-balanced adult with that sort of sense of her own importance in the world
Hmmm, but having her emotional state totally undermined, ignored, and dismissed in lieu of a photo - ie giving her the message that another person's idea of a perfect photo is more important than the people in it themselves or what their feelings are - is going to create a perfectly balanced, emotionally stable adult, hey.
The fact of the matter is that all of the traits that that little girl is exhibiting are the ones that should be valued in children - the ability to express emotion, the ability to be assertive about things being done to her and to stand up for herself, the ability to take herself away when she can't contain her own emotion so as not to inflict it on others. These are all things that should be encouraged in children - they're certainly things that we want adults to be able to do for themselves and the people around them. For example - if she's in a situation in 10 short years where a spotty-faced boy wants her to have sex with him and she's not ready to, and he's pushing the point - do we want her to be too scared to speak out about her feelings or do we want her to be able to say "No! This isn't right, and I'm not going to do it!"
Because the fact of the matter is, all that you're 'training' a child to do by telling her that a photo is more important than she herself is, is to suppress her natural feelings about an issue, and submit herself to anything and everything that somebody else feels strongly about - not matter how unpleasant it is or how much she doesn't want to do it.
That's not what I want for my children.
Children aren't dogs, nor yet possessions. They're people. Little people, certainly, people who need guidance, people who deserve as much respect as any other person - and people who need more protection than big people who, quite frankly, can get over their 'disappointment' at not having the perfect photo.