Serena Colman was an employee of the British Men of Letters.
Background
Serena received three PhDs prior to working for the British Men of Letters. She is first seen at the British Men of Letters compound located in America. Much to her dismay, Arthur Ketch tells her to do some cleaning for him despite her qualifications. Ketch responds by telling her her employers are truly proud.
She is present at the meeting and is introduced to Sam Winchester. She explains Project V and their efforts and success. She says vampires are viewed as terrorists, in contrast to what the American hunters view them as.
While the team is planning for the vampire nest at the More Rest motel to be wiped out, Serena realizes through the surveillance that McGillicuddy is missing. Mary Winchester correctly deduces that the nest they were intending to wipe out has arrived at the compound.
The inhabitants all gather back in the main room and seal it off to prevent the vampires from entering. One of them, a captured vampire, reveals that his father told them where the Brits were. When Serena argues that the Alpha has been in Morocco for at least a decade. Sam corrects her, telling her he saw the Alpha at another location five years ago.
In order to survive, Mick decides to bring out The Colt. However, they need time to make the bullets, so the three hunters are sent out to buy some time. As Serena watches Alton and Mick perform the necessary spell, Pierce Moncrieff returns unexpectedly and slams on the door, demanding entrance. Alton Morehead open it for him. When they ask what happened, Pierce tells them it's pretty bad outside. A moment later, the Alpha Vampire emerges and kills Alton by stabbing him to death.
Serena is initially terrified, but she makes an attempt to attack the Alpha, only to be easily disarmed and bitten in the neck, and subsequently drained of blood. She is the last operative to die in the raid.