Eugenia is a middle-aged woman, and best friend of Gillian Tucker. She and Gillian share Gillian's house and have since the alleged suicide of Gillian's husband. Eugenia is otherwise in dire financial circumstances: her clothes are older and threadbare, she tends to steal condiments from restaurants, and she dislikes going out in public. Gillian has tried several times to set Eugenia up on dates but they never seem to work out. One of these dates was with Gabe McKinley, with whom she was present at Lance Tolkin's death.
When set up on a pity date with Gus, while Gillian has a dinner date with Shawn, she executes a "double pull-back" from Gus' advances, and as a 'get to know you gift' splits a stick of gum with him. He later complains that she smelled of mothballs, which they chalk up to her love of gardening. This fact later proves to be a crucial clue as all the men who seemed to be getting serious with Gillian were poisoned with naphthalene, the main ingredient of mothballs. This probably includes Gillian's husband, who was one of the fatal cases along with Lance and Gabe. Shawn is poisoned similarly but luckily survives.
When Clive Prescott comes to her for her advice on how to approach Gillian with a marriage proposal, Eugenia puts poison in his tea. Fortunately the gang intervene before Clive drinks any of it, and when Eugenia is arrested she claims that she is only trying to protect Gillian because she keeps going out with the wrong men. However, Shawn knows that Eugenia is in love with Gillian and hoped the two of them could spend their golden years together.