Madigan has aspirations far beyond the State of Illinois. It's in her blood.
And filing for Cert (and losing) doesn't cost her anything in her "base". Winning wins her base, and doesn't cost her (much of) anything in her opposition.
Edit to Add: The only thing I think that was keeping her from filing for Cert was the assumption she'd lose after the Heller and MacDonald cases. With the decision not to hear, she gets to rethink that assumption.