Some players (like myself) had the bug where Olena is somewhere out of reach or the marker points to the bridge in Talmberg but she isn’t there. She most likely that died at some point (there’s a bug where she spawns in the air and falls to her death). Thanks to the user spraguep from Nexusmods you now can now (re)spawn her. Just tested it and it works.
Download and install this mod (v 1.24): https://www.nexusmods.com/kingdomcomedeliverance/mods/106
Open console and type: cheat_spawn_npc token:olena
She’ll spawn right in front of you and you can talk to her and continue the quest.
