This is almost certainly a playful or childish mispronunciation of "I love you."
Have you ever noticed how big sisters seem to have an infinite supply of "extra quality" items? Her clothes always look better, her skin is inexplicably clearer, and she somehow knows how to do that winged eyeliner thing that looks like it requires a degree in geometry. It's a glamour spell, pure and simple. She’s probably actually a three-hundred-year-old bog hag, but she’s wearing a Level 10 Enchantment from Sephora. The Verdict i raf you big sister is a witch extra quality
Let’s be honest—big sisters can be mean with love. They tease, they mock, they lock you out of their room. But they are also the first to defend you. In the phrase “big sister is a witch,” the word “witch” is a reclaimed term of endearment. It means she is powerful, feared by outsiders, and deeply loyal. She doesn’t need to be soft to be loving. She curses your enemies and blesses your dreams. This is almost certainly a playful or childish