If she was interrupting the speech, she got what she deserved. If it was just the shirt, I can't agree with the cops decision.
Of course, I also think Cindy Jihad should be tried for treason and shot... but that is not the point.
Listening to Tony Snow, a congressman's wife had a pro-troop T-shirt and was asked to leave as well. AND SHE DID. No fuss. No arrest.