If it is clear that she violated the dress code and then refused to comply with school authorities to correct the problem then she is guilty.
Ohhhh you're makin' me angry.
See, guns don't imply violence. Images of guns don't imply violence. I've never used a gun inviolence, and neither have I seen one (first hand) used in such an application. They're usually associated with celebration, recreation, and physical excellence in discipline - just like a basketball, a hotdog with a soda, and a jetski are.
It's all in the mindset of the administration, and how they want to apply ambiguous rules. The "if they obeyed the rules, they'd not be in trouble" mentality infuriates me, because it's ignoring the fact that hte rules are not only flat out wrong, but are being applied in a fashion to squash unpopular political statements - that is, anything but Leftist agenda.
Using the same reasoning behind banning this purse, a Che t-shirt would be fine, but one which simply said "Che was a murdering totalitarian-wannabe with a hatred for American ideals" would get you suspended - despite the veracity of the statement. It's simple, unbridled thoughtcrime persecution. "We don't want anything which encourages thoughts contrary to our beliefs to be allowed in the school, and that includes an image of a gun being used in a non-violent fashion." The fact that it's a Warhol painting is just icing on the cake, and quite ironic.
This girl is being hung out to dry. If I were the parent, I'd withdraw her from school and let her home school herself (if she's up to it). If I were the student, I'd refuse to comply and tell my parents I'd want to do same. There is no working within a system like this, where the most innocuous actions are taken and misconstrued to imply malicious intent. The best thing you can do in such a situation is withdraw yourself from their institution and let them decay from the inside through their own wrong-headed devices while trying to preserve as much of what as good in yourself as you can.