We lost the battle

I (26F) declare that today is the saddest day of my life. It's the day after Christmas here in our country.

We just lost my little sister (22F) earlier today at 3AM. She was diagnosed with super aggressive, high-risk Burkitt Lymphoma on November 3rd of this year, and now, she's gone.

I know that she's now happy that her suffering is over. She's even considerate to leave us the day after Christmas, so we would always be able to celebrate without being too sad.

I'm just lost for words. I don't know what to do anymore. I raised her like my own kid, and it was always the three of us (me, her, and our youngest sister). I never really understand why it had to be her.

EDIT: Thank you all for your kind words. I'm also praying for you and your families strength.