From the AP (emphasis added)

Herb doesn’t recall exactly what she said, but she admitted letting more than a few choice words fly near an open bathroom window Thursday night.
Her next-door neighbor, a city police officer who was off-duty at the time, asked her to keep it down, police said. When she continued, the officer called police.

Mary Catherine Roper, an attorney with the American Civil Liberties Union in Philadelphia, took issue with the citation.
"You can’t prosecute somebody for swearing at a cop or a toilet, she said.

See Chaplinsky v. State of New Hampshire, 315 U.S. 568 (1942), in which a man was prosecuted for swearing at a cop:

There are certain well-defined and narrowly limited classes of speech, the prevention and punishment of which have never been thought to raise any constitutional problem. These include the lewd and obscene, the profane, the libelous, and the insulting or "fighting words" those which by their very utterance inflict injury or tend to incite an immediate breach of the peace. It has been well observed that such utterances are no essential part of any exposition of ideas, and are of such slight social value as a step to truth that any benefit that may be derived from them is clearly outweighed by the social interest in order and morality.

While LexisNexis claims that Chaplinsky has been superseded by statute, that's only true if a particular state has altered its statute to require a threat or some other element in addition to personally abusive epithets.