>>537790182
She never broke up with you when you resisted Bhaal. That line was never implemented in the released version of the game at any point. It was added as a bug when they altered her act 2 recruitment scene and was promptly removed again less than a week later in a hotfix where they confirmed again that it was a bug. If you're interested, you can even find the post.

Minthara hates that gods use mortals and toss them aside due to her own experiences with Lolth, and she sees the same pattern forming with you and Bhaal. She prefers when you reject Bhaal and make your own decisions in life. She is sad to lose the patron god and the slayer form because these are forms of power and support, but ultimately her personal beliefs regarding her resentment of the gods treating mortals like playthings wins out and she approves.