So I did some of the heavy lifting in tracing the bug for you. It is tied to the script that recruits Jaheira to the party and sets her faction. All party members get a "CompanionXX_UUID" set and hers is stuck with "ACT2_SCE_EpilogueFaction_9c896609-f2f6-4f1a-8967-c83140977975" which is an act2 faction for her.
EDIT: I even did more work for you. It appears in the code that her faction is suppose to be set to "Companion15_9a7c52c8-ca88-4493-bca5-9b917494c94c" but something is not doing that. Minthara somehow is getting assigned "Companion12_aeaf8c61-8ff3-1bc2-18fc-7da29495fc68" in my game and I cannot find where you do that so currently this is outside of what I know or I would fix this for you.
Fix this please.
In the meantime, I have created this temporary solution for anyone who has BG3SE. This console command will fix this. DO THIS ONLY WHEN JAHIERA IS IN YOUR ACTIVE PARTY.
Osi.SetFaction("S_Player_Jaheira_91b6b200-7d00-4d62-8dc9-99e8339dfa1a","Companion15_9a7c52c8-ca88-4493-bca5-9b917494c94c");