If their "No Props" policy is an actual policy, and they enforce it evenly, then that's what we want: Equal Under the Law. No Two Tier System. It sucks that Patriotism is the topic here, but that's that.

Pretty sure that Flag Code says that the Flag is not to be worn. And I'm not sure if whatever she's sitting on there counts as the Ground...

I love what she's going for, but honestly, it's important to not only love our Flag, but to Honor it appropriately. Were I her, I'd readjust, and find some other way to stick it to the man. Perhaps find a rather patriotic location full of American Flags, and take a picture there, while wearing clothing with American Flag Patterns on them. That would satisfy the "no props" rule, and also serve as a resounding "Fuck You" to the commies.