I'm also regretting not recruiting her, at least now that I'm seeing all the content coming out for her. i was hoping I'd get to see the other guy's shortstack imp in the future at the time.
Attempted changing some flags around in the Save editor to see if i could force her to appear in the wayfort, but unfortunately without a proper understanding of what flags are required and whether or not it's even possible to force her to appear via editing flags, we might just straight up be SOL.
i do have a save from the quest in question... unfortunately it looks like it was from after i completed Tharsus' task. alas.
Best hope is that maybe someone who DOES have Olivia can look through their own flags, find what flags for the dungeon, Olivia, and Tharsus are on / off, and then share those. Maybe we can compare those flags with our own, and see if matching them from that save to ours would cause her to appear.
or we might just be SOL. Entirely possible. in which case, nothing we can do but live with our life choices.