It doesn't look like a bug nor like earwax to me. It looks like a piece of something like a paper, or maybe a piece of flower leaf that fell inside the ear.
It doesn't look like a bug or wax to me either. I suppose your sister could send that pic to her vet (if they accept pics) and ask if it looks familiar to them, but I would guess they are going to say no. Any other symptoms, like the cat scratching its ears, or shaking its head?