This Eileen quest seems buggy. I talked to her in the Sewers in the first part of the game but never found her anywhere else. I explored a lot of the Cathedral area and eventually moved on and defeated the optional boss,
. I realized I never lit the lamp for Tomb of Odeon and wanted to see if Eileen was there so I walked there from the Cathedral Ward and activated the lamp. Eileen was nowhere to be found.
I went back to exploring in the Cathedral and cleared most of the area. I didn't want to fight the boss here yet so I kept going and eventually found a path leading to a cave. I had amassed around 30K echoes so I decided to use a 'Bold Hunter's Mark' to teleport back and spend them before continuing.
I forgot that the last lamp I had activated was the Tomb of Odeon and when I awoke, I was immediately jumped by a NPC hunter. A short time into the battle, Eileen runs out and engages him. I dispatched the hunter and talked to Eileen. It looks like the next step comes after the boss,
.
I had been through Odeon a couple of times prior to this so it seems odd how this quest phase finally triggered from warping via the mark. I never engaged the boss of the Cathedral area (some people suggested this may be the trigger) and I never found Eileen anywhere else in the Cathedral area where she supposedly tells you about the hunter in Odeon and gives you an emote.
Meanwhile, my wife is also playing the game and missed Eileen in the sewers. She checked prior to
and after
and cannot find Eileen anywhere in the Cathedral zone or at the Tomb.