They may have been going for a Janet Leigh in Psycho angle there. It was pretty shocking that someone perceived as a main character is so abruptly killed off. Maybe we’ll find out more about the character in Rogue One?

When have we ever had a definite female droid personality in the OT? There were female looking droids in Episode III, but as most of those scenes were cut, they were mostly in the background of some Coruscant scenes. They looked too advanced for the prequel era anyway.

I did notice R2-KT had a cameo in the film though.