The circumstances surrounding Vanessa's death are not known, however Cecil mentions there being a clump of hair and skin on some shattered glass in the Desert Bluffs' producer's studio and Kevin also mentions Vanessa's head bleeding badly from an accident while building a shelving unit.
It is also unclear when Vanessa died, as Kevin mentions she has already been dead for "many years" during the mayoral debate. 
Relationship to Kevin Edit
Unlike Cecil's interns, Kevin is hurt by Vanessa's death and talks about her as if she is still alive, even when acknowledging that she is dead. It is unclear is they were friends outside of work, but had a good relationship inside of work.
Sandstorm 19B Edit
Kevin first mentions Vanessa in Sandstorm (Part B), when he says that she mentions "Sandstorms can do damage to cars" and later that she is taking calls (specifically one from Lawrance Lavigne) and keeping an eye on Facebook and twitter. He shows her a video of cats and then asks her to tweet it to him. Later in the episode, noises can be heard in the background and Kevin says that the noise is Vanessa and her double. He later mentions that one of the Vanessas has been injured and her head is bleeding. Kevin believes this to be the double. This mirrors Cecil's later mention of there being skin and clumped hair in the window to the control room. It is unclear if Vanessa killed her double (or visa versa) or if this was already there and the noises were from another source (as Kevin mentions Vanessa and her double during Taking Off and mentions Vanessa being dead during The Debate).
The Debate Edit
Vanessa is mentioned in the Debate when Kevin mentions wanting Cecil to meet Vanessa because of her morning jokes and wide smile. He talks about how he would imagine the her skull. When questioned as to why he couldn't bring Vanessa, Kevin says she "Died many years ago" and that he "doesn't like to talk about it much". It is unclear how much time has elapsed between the sandstorm and the debate in either Night Vale or Desert Bluffs.
Taking Off 70A Edit
Kevin mentions that he can see Vanessa in the producers booth and that Vanessa and her double are working at the station in Desert Bluffs Too as they are "a bit under staffed". He says they are acting as his producer, head of marketing, and answering phones.
Intern Dana Edit
It was believed that Vanessa was Dana's double and that Dana had killed Vanessa during Sandstorm Day, which in turn affected Kevin severely, however during the events of A Matter of Blood Part 2, Dana's double is mentioned several times as 'Dana' and Dana herself is unclear on whether she is the original Dana or her double.