It may feel like developing slow because after the romance scene in Act 1 she just does not spend time with you or stay in the camp so narratively it would be difficult to drop in cue's without breaking the immersion to let the player know you are in a relationship and I 'm glad it was decided to keep it the way it is now, it will just have to take players own inlellect to grasp at the relationship status exactly as you get the dice advantage later on during rescue scene.
Given the myriad of dialogue choices and if you drop into her fears and fail the dice check for example, game flags you both as not in relationship and you get disadvantage on the dice checks during rescue scene,.
So one could debate that if she truly is not herself none of these relationship notions would even matter at that point as Minthara would not care and just busy enjoying the trip, other than mechanically in the context of gameplay element which I doubt its solely there for.
While most of the comparisons are okay'ish I feel comparing Minthara to Chop to be unfair,
his mind has physically been carved out and is quite brain dead like a robot, Minthara doesn't reach that condition until after she's gone through with her punishment in Moonrise Towers, which is an option for the dark urge to finish and earn an inspiration point in the process.
