There is more option to deal with girl, but some them are class specific and some depend on your attributes and skills.
As cipher you can wipe girls mind somewhat clean so that she don't remember that his father sexually abuse her and you can convince her to go back to him or you can tell her truth or something else.
With high enough lore and intellect you can understand what is going in the ritual, which gives you more options
You can let cultist finish with ritual and let girl go back to her Lord father as double agent (then you can reveal that fact to Lord so that he can decide what to do and even persuade him to take her to animancer in Defiance Bay so that they can search cure)
And some other options
So there is more than two options to handle that quest, but those options aren't necessary always open as you haven't find necessary information to unlock them or you don't have high enough attributes/skill or you have wrong class.
But there is probably options that you as player would want to do/say but game don't offer corresponding option.
How did you convince her to do that? Because every time I pick the cipher option the only thing I can do after the fight is pick several options for her to run away to. I don't see any option to convince her to go back to the lord.