Here's what I think: the way Hye Shin's putting it, she did it on purpose. (She said she didn't think it would blow up this big.) She might've wanted to slowly spread a false rumour about Da Ae, by telling her friend who would tell other friends and so on. That way, not only the rumour would be distorted and would greatly harm Da Ae's reputation, it would also not be linked to her in any way, due to all this rumour spreading.
All in all, if my theory's true, then Hye Shin's very wicked.