In the defense for Haruko, she's clumsy, absent minded, and not the sharpest tool in the shed. In that case..... I think it's her personality that wants others to spoiler instead of her spoiling them.
She gets like that occasionally. Like when she walked by a blood drive and started talking about how useless she felt, since giving blood should be something even a NEET could do for society, but she's too scared of needles.