Jarvis on Monday fired back, saying that Cowley's termination was done in an "unofficial email."
"Detective Cowley's termination is not valid until he or his attorney have been properly served with the City's Decision to Terminate," Jarvis wrote in the letter. "As such, Detective Cowley's benefits, including his salary, should not be interrupted until compliance with proper termination requirements have been met."
The city was supposed to either hand-deliver the notification or mail a certified letter to Cowley's home, Jarvis said in a phone interview.
The city had sent a letter at the same time as the e-mail, but because of a clerical error, the letter was not certified, said city spokesman Aaron Crim. By 4 p.m. Monday, the city had rectified that and will extend Cowley's salary and benefits until the new letter is certified, Crim said.
Last week, Jarvis alleged that Cowley was the "fall guy" for the entire Neighborhood Narcotics Unit, which has faced allegations of misconduct, corruption, mishandling evidence and systemic cover-ups. Seven of the nine officers have been restored to active duty after being on leave for months.
Detective Kevin Salmon, who was also involved in the Willard shooting, remains on paid leave pending the outcome of that investigation.
Jarvis said Cowley was the victim of no supervision and training on how to become an undercover officer.
She said she wants to appeal the termination, but said she cannot do so until West Valley City follows its own rules and procedures.
Tribune reporter Michael McFall contributed to this story.