I'm always drawn back to the old unfinished Byrne fable, "The Last Galactus Story." Since Time is an illusory construct, who is to say that Galacta couldn't be the daughter of end times Galan and Frankie Raye (Nova II) existing in the here and now? Nova ultimately would have evolved into becoming the next Eternity/Infinity according to Byrne's notes. It might make for a sweet slice of continuity pie if Nova becomes the mother of the next omniverse while also giving birth to its next Galactus in Galacta. It would certainly answer the question, "Why is Galacta here?" To meet her father, of course. Every little girl needs her father.