I'm not criticising a member of the armed forces here for what the do, merely the idea that their views on remembrance might be superior than someone else's views.
We all know the armed forces is a mixed bag, those are there through great humanitarian urges, or at the other end, a love of violence and guns, who knows. (I know people in the armed forces, who went in with very different motiviations).
I don't agree that the remembrance events are equivalent to a funeral, they're for the nation to come together to think about the service of people who died, but also to think about war and for some, that includes thinking about its futility. Wearing a white poppy seems a very reasonable thing to do.
I can't imagine anyone who actually served in a war would be upset by a white poppy.
It sounds as if the OP's daughter is thinking about these issues, and she should be very proud.
What is far, far more offensive is the hypocrisy of those who wear their poppies for one day (or a week a year), but don't think about the reasons for war.
Surely the lesson of WW1 was that it was a futile conflict.