Why not? Maybe T'Rul was suspect politically, and they sent her with an obsolete cloak to test her loyalty. Maybe they were even afraid anyone they sent to a babysit the cloak would defect, so sent someone unimportant with old equipment.
Anyway, I don't see why the rank of "sub-commander" has to mean she's a person of any importance in the military. It could've been a bonus given as an incentive for her to go play with the enemy.