Ok after futher testing I found out that you get the quest box choice + the strength one by threatening to cut her head and then lose your intimidation roll.
Go figure
Did it like that and game gets bugged out.
Ofc, both hairs are available, but Mayrina vanishes even then when talk about deal with hag is over. Also Hag Ethel vanishes along with Mayrina.
On top of that the Questlog and the Save Mayrina Ques is also completly deleted from log. not hidden, plainly deleted.
Either its not a finished Questline having this solution and Larian didnt wrote another ending and made cutscene and anything onward from that leading to Baldurs Gate and Ethels Sister Hag M.
or
it is really a bugged out Quest then.
PS:
you forgot to mention that after losing intimidation check you need to choose Power over Mayrina to get the selection screen. Then saying goodbye to Ethel in aany of the 3 dialog choices. This leading at least some of your companions to DISSAPROVE your Action.
So why lose the Intimidation check anyway. Just let Ethel go with Mayrina by only chosing POWER option.
You will get both Hairs in any way bec. it seems its a bug in patch 6 that you allway get both hairs by doing so.
PPS:
My assumption of Release Version of this quest line is that in any way this Qeust leads to something up in Baldurs Gate.
Either you get the +1 Ability early here and have to conclude the problem with Mayrina in Baldurs Gate later somehow learning she went into city with a UNDEAD and something terrible happens because yyou let her go back with her dead husband (provided you chose the right Dialog options and revived him with Wand and gave it to Mayrina)
The other End would be that MAyrina is giving Birth in Baldurs Gate and Hag Sisters will be met later to have a questpart to find a solution to either support the hags again or something else. Both ways somehow netting you an +1 ability score later in game. Maybe even a spell for fully reviving Mayrinas Husband too.
