Confused how people think the minthara change is OOC
She specifically tells durge she would break up with them if they refused godhood. That was already in the game, it's just now she actually follows through with it.
Here is a copy from the exact conversation branch:
Minthara specifically tells Durge during a previous conversation that she would break up with you if you rejected your birthright because "To reject it would be to reject godhood. You would lose the possibility of shaping the world to fit your desires. And you would lose me. Bhaal is not like the absolute. He will not control you... he will unleash you"
So minthara fully is on board with bhaal because bhaal doesn't enthrall his followers.
Mintharas character is not "against the gods". It's against gods controlling her and/or her SO.
However, Bhaal doesn't really control his followers. They notoriously do whatever the fuck they want and as long as they are killing things bhaal never cares.
This is evident about her feelings on the matter from the quote above.
So, if anything, her NOT breaking up with durge if they don't accept their godhood was always out of character. She was just bugged so she never followed through with it before.
Direct from the DnD wiki:
" He is a murderous and sadistic deity who uses his dogma to encourage his worshippers, composed by assassins and criminals, to commit murder on innocent people ... "
Bhaal does not control his followers, he lets them go fucking crazy to do whatever evil bullshit they want (so long as they're killing).
It makes complete sense that minthara would be pro-bhaal. Bhaal is nothing like the absolute or lolth in that manner and would not seek to enthrall either of them. Again--further confirmed by her own dialogue addressing this exact topic.