Siblings post photos of each other with the caption, "I RAF you, even though you're a witch."

Weeks later, Rob stopped showing up for work. The cigarettes grew dusty in his pack. He started leaving messages on my phone with only a single line: "She remembers too much." Once, he wrote: "The coin is warm."

She taught me small things—how to coax a lost cat from behind a radiator, how to tie a knot that keeps nightmares at bay on nights when the moon is thin. She refused, always, to grant me the true power she wielded in the house beyond the gate. "You're not ready," she said. "Power is not a tool. It's a conversation you should be prepared to end with a no."

When they came for her, it wasn’t the wolves in suits. It was the priest who had crossed himself, now wearing a different kind of certainty. He came with candles and a book that smelled of lemon rind and old prayers. He demanded, in the name of saving people's souls, that she hand over her ledger.

If you are looking for a story based on the general idea of a younger sibling discovering their older sister has magical powers:

If "I raf you big sister is a witch" is a specific copypasta you found, paste it here! I would love to analyze the text directly, decipher the typo, and tell you why it works (or why it's a glorious disaster).