Jenna Villette is a friend of Damian Boyle. Kalinda Sharma first met Jenna when she arrested Kalinda, as a favor to Damian. Kalinda was following Damian as a job for Diane Lockhart. Jenna doesn't let Kalinda go, because Damian asked her to wait so she has to sit in holding all night. But this ends up with Jenna and Kalinda in bed at Jenna's apartment instead.
When Will dies Kalinda calls Jenna for help, to come in where it is only cops allowed. and Jenna helps her finding out what happened.