It is not a "crime." Yes, it is corrosive of good order and discipline, and the failure to stand when told - I am presuming that a direct order was given here - is disobedience of a direct order.
I am presuming that this was a first offense. And brig time for a first offense of this nature is somewhat over the top. There are ways you deal with first offenses of that kind. First, you tell her chief petty officer that it is his/her job to get her in line. Extra duty, etc. If there is a second offense, more of this, then it gets more serious and escalates rapidly. It can escalate very rapidly.
But the goal is to instill firmness, discipline and guidance. Not destroy someone's life for a momentary lapse of judgment with no real adverse consequences except the worry that you cannot let this kind of behavior continue.
Unfortunately she’s a reservist. Otherwise she could count on restriction, extra duty and a suspended bust to next lower grade, and I’m betting she’d be assigned to assist in executing both morning and evening colors. Any problems and, as you stated, ‘it gets more serious and escalates rapidly’. Next trip to CO’s Mast and she could leave as an E-3. For an Intelligence Specialist, she’s not particularly bright. Just read she’s claiming the Navy revoked her clearance, which effectively ends her career as an IS. Smart move by Navy if true.