I’m still not convinced she’s insane. Insanity implies that she has a lack of control. She just seems like she enjoys killing people on a whim, and would rather get drunk and sleep with her men than actually run the kingdom.
@Zephyr247 The alcohol and sex sounds to me like some sort of self-destructive coping method for her PTSD or what ever mental illness it was OG Yulia got from the war