On top of all her other unprofessional behaviour in this episode, Tiff tells Hobbs' widow about a terrorist suspect being in the USA. That information was presumably confidential. Leaking it to a member of the public could compromise their efforts to find him.
Kelly says that they couldn't get info about a WhatsApp user without a warrant but added that he could follow the IP address. He does that and immediately has all of the user's information.