Re: TNG Cold Equations Book 2, Silent Wpns Nic-Picks -- SPOILERS
I think also it is in Picard's character to find and nurture potential. His relationship with Chen in a way reminds me of Ro Laren. He saw there was more to her than what everyone else sees. Picard might see the qualities of leadership in her and with everyone else occupied with the mission felt this would be an opportunity for her to get some experience. As a contact specialist she is trained to be prepared for unexpected situations and her outgoing personality lends towards quick thinking on her feet which are attributes essential for someone in command.
Senseless is on vacation, Im just filling in....