Because let's be honest here : it doesn't matter if Starlight had won or not, the mane 6 still have a lot of connections, including one knowing why they're gone and having a map with the location at hand.

What if, some time after the events caused in the Everfree forest by Chrysalis, the former Queen received a visit from a certain draconequus who didn't take the time to gloat to her after her previous defeat ?