(English is not my first language! Bare with me, thank you!)

I (21 F) am not really a big fan of confrontations. I avoid them like the plague, especially with family fights.

However, I have this sister (23 F) who has a deep hatred towards our mom. She claimed that it's the noticeable favoritism, but I dont think that's the case since our mom tries her best to love us all equally. I think she was holding a grudge against her back when she BEGGED our mom to let her transfer into a different college course in a VERY prestigious university that we obviously cannot afford, so my mom told her "no" and — 'til this day — my sister still accused her for forcing her to study in a "peasant" university (public university).

My mom would mentioned to me that my sister would make her feel humiliated, especially the "dress incident". This is when my mom found a beautiful dress (she does not know who it belongs to, but it was a gift from her sibling) hunged up for so long in the clothing line and decided to try it on. She showed it to my sister, happily wearing the dress, until my sister angrily yelled at her about "stealing her stuffs" and tried to strip my mom out of the dress until she was left with nothing. Though she claimed that she doesn't remember that, my mom was deeply traumatized by that event.

For me, she would make me her "servant" because I'm the youngest and she claims to be "busy" when all she does was sleep and play games whenever I do her chores despite having a ton amount of school works. I complained that to my parents but told me that "siblings should help each other out". I didn't like the response but suck it up anyway since I dont like to stir up any fighting over some chores.

Until I was at my final straw.

Sunday afternoon, me, my parents, and siblings are running towards the church entrance cuz we were already late. Then, we just heard my mom scream and a loud thud. Turns out she tripped on the sidewalk and hit her knee first. My sister, annoyed and pissed, yelled at her loudly in public, " God, mom! You're so humiliating! Stop being such a crybaby!" We were shocked. My dad glared at her while my mom was pissed at her but bite her tongue back.

I was very pissed as well. You're own mother just tripped and that was your response? I just wanna punch her so bad!

While my dad was helping my mom up, my sister just angrily about to enter the church. To describe the entrance, it has some stairs with 5 large steps before you can enter the door where the ushers are, and being the angry daughter that I am (since my mom was being disrespected), I just see red and quickly walk behind her, then grabbed a fistful of her hair and pulled her down the stairs to the ground. I also "accidentally" stepped on her newly painted nails, while she yelled "What the fuck was that for!? Remove your damn foot from my hand!" And other complaints that I was ruining her nails.

I just scoffed and replied, "God, you're so humiliating. Don't be a whiny baby"

I do remember she got mad and a fight almost happened before my dad intervened and telling us to "act like adults" and proceeded to church like nothing happened.

Though we both got scolded by our actions the moment we got home, my mom privately talked to me and thank me for defending her, but she gave me a lecture how I should not pick a fight with my siblings and told me to apologize later since I started the fight because, as the youngest, I should love and respect them.

I do feel proud of what I did, but I also feel guilty that I did that. AITA and must apologize or no?

(Im so sorry for the long lengthy post huhu i just wanna vent)

Edit: I'm seeing a few negative comments about the church. Do not bring the church into this. We're humans and we still commit mistakes, we're not perfect. I'm not perfect and I let my emotions blind me to do that negative action in a public place that HAPPENED to be the church we were going. It has nothing to do with church or their teachings. Just me, being blinded by my emotions, and the person I got physical with. That's it. Thank you.