Blue Star builds up to the reveal that Femshep, in the years between her turning 18 and joining the Alliance, worked with Blue Star as an ambassador. She was, by far, their most popular ambassador, and her leaving dealt a noticeable blow to their operation.
They have brought in a handful of new ambassadors, but success has been limited. Shortly after the destruction of the Normandy SR-1, they picked up Tali’Zorah as their current ambassador. The Migrant Fleet was stricken with famine, and when it was explained to her what her duties would be (and enticed by the new experiences their immunoboosting treatment would give her, by letting her leave her suit safely), she eagerly accepted the role.