Helping Little Sister

🇰🇷Deborah★★★🇰🇷
Hey everyone.....
This has been weighing on my mind very heavily lately and I kind of wanted some advise on how to handle the situation.
My little sister came out as pansexual a couple weeks ago and at first? I was the only one in my family who knew about it. She was really scared to tell me, but I started crying, just relieved that she was willing to tell me something so personal when she's been lying to my family about it.
I told her that isn't something I would choose for myself, and I love being in a relationship with my husband. But, I love her as well and would support her in her decision to choose how she will.
Fast forward a week or so.......
My family part of the Mormon church, (please no bashing on the religion~ just to give some clarity) and my parents get a call from our bishop saying she had posted something about, 'being a supporter of the LGBTQ+ community in the Lord's house' and my parents busted a gasket.
I was shocked....watching my mom suddenly fuming, face turning red....before suddenly turning pale and bursting into tears.
We believe marriage is between man and woman? But I know plenty of members who struggle with this who sometimes choose to not act on those feelings. But my mom was more worried about her 'eternal salvation' than anything else at the moment!
I was furious and anxious....and scared....furious that *that* was what she was worrying about, anxious and scared because....well....I knew everything that was going on without telling my parents I knew until after they found out.
shakes head- Its none of my business....telling them something like that. That was my little sisters thing to share.....but I wonder often if I was in wrong for feeling that way...
She lies to my parents because they didn't believe her when she told the truth....its not my place to share her information.....
....but what can I do to still show the needed support to both parties? My parents and my little sister?
She needs someone to talk to....but I don't want to continually feel like I am betraying my parents either.
....any advise?