Does Chen feature in Destiny?
Not really, no. She has a few "walk-on" moments in books one and two, and a cameo in book three, but she's not a major player in the trilogy.
Part of the reason for that is that I had finished the detailed outline of the trilogy and was already writing the first book when Christopher developed the story for Greater Than the Sum
. To help set up the trilogy, he established some of my new characters (Choudhury, Elfiki) and tied up some loose story threads related to the Borg that I didn't address in the trilogy.
By the time I realized how important a character T'Ryssa Chen was to his story, it was too late for me to retrofit her into the trilogy in a meaningful way.