SOLVED. Wattpad Romance/Action with MC being female and she has a fraternal twin (names should be Astrid and Ashton?) and they have 3 other friends whom they were at an orphanage with...

[Lady]

SPOILERS AHEAD!!!
I don't remember the author.

So, there's a book I've been looking for, and I think I read it in 2018. In the book, her name is Astrid I believe, and she has a twin.
They were adopted by a rich family, who were in an elite circle of sorts (which sometimes dealt with rare archaeological items), and their friends from the orphanage were also adopted by their parents' friends.
Her love interest (whose name I think is Damien) was one of her childhood friends from the orphanage; (this friend's family has a tradition of giving necklaces to their significant others while they get a tattoo of said necklace).
In short, she had to leave her family to train as an assassin for some years for their protection, and her family thought it was a kidnapping.
When she finally came back, she was 17 or 18; they then sent her to the private school the other kids were attending which was on a remote island.
She also had a bounty on her head in the assassin world after escaping. She fights well and was kind of traumatised from almost being sexually harassed by some of the other assassins.
During the holidays she went on a trip with her brother and their friends.

Very important: she and her twin were discovered to be their adopted parents' real children, whom their parents thought died in a fire when they were babies.

[Lady]

I've found it. It's called Crossing Borders by @Triszjhkha on Wattpad.