Shouldn't be possible in 0.17.9 - only in the initial bugged release of 017.8. If you managed to do it in 0.17.9 please let me know the steps you took to do it.
Viewing post in WEEKLY RELEASE - v0.17.9! comments
Well I beat the next boss with seduce put her in the dungeon I went to recruit her not sure if I did it once or twice with the persuasion then Chelsea appeared on the captive list I clicked her and the scence played out and she got recruited again I now have two of her icons on the prepared menu and I checked I am on version 0.17.9-pc windows version