In my opinion the principal rights here arise under the Fourth Amendment. The Fourth Amendment prohibits unreasonable seizure without a warrant. Warrantless arrests such as here are presumed unreasonable unless the officer has probable cause to believe Evelyn was committing a crime. That crime would be obstruction, ex. 18 U.S.C. 1509 or 1503, or a state law equivalent. Excessive and disproportionate force, as here, can also make an arrest unreasonable.
A First Amendment claim is harder to make because, per the Castañon Nava consent decree, ICE is not supposed to pick up individuals for deportation without a warrant absent a clear flight risk. So going and warning people that ICE is coming for them could be argued as obstructing law enforcement from executing warrants, or from complying with the decree, which is unlawful conduct rather than protected expression. Whether Evelyn knew about the consent decree is irrelevant in asking whether officers violated her freedom of expression rights.
A Fourth Amendment claim, however, would require the officers to show probable cause not only that Evelyn obstructed the enforcement of a court order, but that she did so intentionally (obstruction generally requires intent). Assuming DHS shows probable cause for arrest, they would still have to find a way to argue that dragging Evelyn out of her car and kneeling on her neck was objectively reasonable in response to a relatively low level, nonviolent crime of obstruction.
~Max