I feel like a good way to do this would be to have her try to escape after losing the battle at the Grove
As it is currently, she sits on her perch and watches the fight only joining in once all her troops are dead and there's no chance of victory. It feels a bit OOC for her to do an idiot death charge like that. Why wouldn't she be more pragmatic about it and try to escape the bounds of the combat area instead?
She'd make her escape and return to Ketheric to petition for more troops only to be reprimanded for her failure leading to her usual Act 2 introduction
Pretty good, but how do you make it so she doesn't instantly blow your cover away, since it was you who betrayed her in the first place? Do you want them to just skip that Ketheric cutscene entirly?
There are two places in that conversation where you can pipe up and have her notice you.
The first time is right after she's asked whose to blame for her failure in which case her trying to shift the blame could be read as an act of desperation since True Souls aren't supposed to have the level of autonomy the party does. Her accusation would seem ludicrous
The second time is after Ketheric has sentenced her to death. If you select an option that supports the verdict she might lash out and accuse you but, again, it could come across as sheer desperation especially as she's being dragged away
And if you select an option to defend her she might be confused by it but I doubt she'd accuse you while you were negotiating for her life. At that point she's despairing and begging for a stay of execution and your character is handing her a lifeline