Background
Originally from Ryloth, Tajil's clan fell out of favor while she was child. Though never especially successful, it was not until the dawn of the Empire that the Tajil's lost enough ground favor to slip into the undercaste.
Average by Twi'Lek standards is enough to be pretty by galatic standards, Dia met the same fate as many other females of her species and was sold into "indentured servitude." She was inquisitive and educated prior to this ill fate, Dia learned a fair amount of Ryloth's and offworld biology thanks to her father's medical practice.
Dia was fortunate enough to end up in the Rebellion, but her unit was wiped out. A combination of luck and skill kept her alive until she was rescued. Unable to retake the field any longer, she seeks to free her family by buying them out.
There's just that problem of credits...
Motivation
Freeing her family.