The planet of Colstev might be a good place to start.  In the source book Age of Rebellion when giving the example of the Diplomat Jin-Rio's origin, Colstev was one of the locations of Imperial atrocity when student and local protestors gathered at the University of Zin-Ro.  The Empire deployed a full battalion of AT-AT's and their accompaniment of Storm Troopers, killing hundreds.  SOunds to me like an event which could bring us together, everyone loosing someone, and at the same time proving our worth to the Rebellion as we aid people in getting off the planet, allowing us to bring the starship into picture.  It could be a model of which Tina and Miria are familiar with and have served on before.