Should I (30M) apologize to my older cousin (45F) for....everything?

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I (30M) am ethnically half-Korean, half-Japanese, and here in Canada, I grew up attending a Korean church for the first 18 years of my life. I have since left the church, and although I don't hold any negative feelings towards the faith, I no longer believe in a God.

My female Korean cousin (45F) also was born and raised in Canada, and she grew up not too far from where I lived as a child. She attended a different Korean church which was related/connected to my church. She's not a Christian anymore either, and she left her church shortly after the events that I'll be describing here.

Back in the summer of 2009, when I was just a boy and my cousin was a 28 year old grad student, she volunteered to attend my church's summer retreat, which I was a part of. I did not enjoy those retreats, in fact I hated them. My cousin knew this, and she came along specifically because she wanted to keep me company and to make the whole experience go by faster.

During one of the days in the retreat, my cousin and I went on a hike along with a team of boys my own age (grades 7 and 8). During this hike, my cousin was the only adult and the only female. She wore a plain white tank top and jean shorts, and the boys kept on pulling her bra straps, or trying to jump at her and lift her tank top up or yank her tank top off of her. Eventually she started crying, and she couldn't stop crying for the entire day. I had Facebook, and one of my friends who was on that hike took a picture of me and my tearful cousin together. That picture is still on Facebook.

In 2018, now a university student and an adult, I was/am part of a group chat with 3 of my old high school friends, all of whom are guys like me. They started hitting on my cousin in the chat, and so, almost 10 years after that disastrous retreat, I jokingly sent them that picture of her taken in 2009, of her wearing the tank top and crying. I told them that this is what she'll look like if she finds out what they were saying about her in the group chat.

Now that it's 2026, I suddenly felt a pang of remorse about everything that happened both in 2009 and for the pic I sent to my friends in 2018. My cousin and I keep in touch still, and she's STILL traumatized from the hike. She's clinically depressed these days even though she's got a successful life. If it helps, should I sit down with her and apologize for stopping those boys? Should I tell her that I sent the pic of her behind her back?