Chosing to do a cover on her debut album is tricky, and leaving it up to public vote has some merit, but I think it would be wiser for her to think hard about it.
Two of Dilana's best rockin' songs, Lithium and Zombie were pretty much carbon copies. That goes for Can't Get Enough. Her Cats in the Cradle, although well composed may still be too tame.
Covering Creep would be interesting, bonus since Lukas did it, and she "encouraged" him to take it.
Since she's collaborating with Gilby, why not see if Heart would let her do one of their songs?
Crazy On You, Barracuda, or Zep's Rock and Roll