My girlfriend received a ticket in the mail over a month after being stopped. Is there a statue of limitations on how long an officer has to file a citation in the state of PA?

Usually one is handed a citation after an officer stops you and signed by him on the spot after he explains why he is giving and if not paid, a reminder comes in the mail. Could the original have been misplaced ? I know this doesn't answer your question, but I don't think statutes apply in this case and you should phone the court house named on the ticket.

Yes, it is one year.