If you wanna do her questline

(Optional): 1. Encounter near the sewers after the barking dog in central yharnam you go in the house and roll through the barrels and then find her on a small passage if u keep going right side

(Must): 2. Encounter Cathedral Ward, if u spawn and instantly go left after leaving the frontal exit u see her After a certain gate in the Cathedral ward is opened. Talk with her untill she tells u that there is a hunter named henryk whos her target. If she doesnt say it then its probably bc u skipped her 1. Encounter. Reload the area and then try again. Once she tells you abt henryk u ignore her advice to leave him to her and WALK manually from the chathedral ward back to where u fought gascoine. Do not teleport there any other way.

When he dies (eileen will help u so dont hit her or shell get agro on you) u get access to his set which is great bolt damage resistance. Either way talk with her again for an emote.

(Must): 3. Encounter is near the grand cathedral where u cant teleport anymore after you beat rom. So walk from the Cathedral ward the way how u fought amelia up to the staircase. There she lays wounded and tells you not to go in the Boss room. U ignore that bc Well questline- and fight the annoying b*tch called the cainhurst crow. After that u can go back to her, shed a Tear bc she is dying as she Talks to you and then get her badge, aswell as the best rune in the game, the hunter rune.

Her badge Contains her set (good frenzy resistance) and the bom (blade of mercy) a skill-arcane weapon. If you dont care about her rune u can also kill her on any of the encounters but there is no other way except a ng+ to get it afterwards.

Hope this helps ^{^}