Well she was arrested on an outstanding felony warrant.
But most countries have limits to free speech. Interesting though that the USofA continually seem to claim their version is totally free. Seems it's fake news.
Free speech is not an excuse to use obscene language, and anyone displaying offensive material can be asked to take it down without it impinging on their right to freedom of speech in a civil manner.
Her arrest was not related to the sign and was not an attempt to shut her up, it was for a previous crime. Just a fool who got was she deserved.
a local sheriff warned that the driver of the pick-up truck could be charged with disorderly conduct.
even in America, freedom of speech doesn't grant the right to shout "Fire!" in a crowded theatre. None the less, she wasn't charged with disorderly conduct, but for using fake ID. So her right to free speech hasn't been abridged.