Not sure what this is saying, but I'm pretty confident it's something along the lines of "What on earth is my sister doing?"

I think it says something like "Satori noticed the giant rice ball, but she pretended not to see it."

fuzzygnome said:

I think it says something like "Satori noticed the giant rice ball, but she pretended not to see it."

That comment was before translation, but you are correct.