Why would this be difficult? They have dealt with a progenitor race, as well as multiple other oddities across the galaxy but
this is the line that they wouldn't get?
I love how dismissive this attitude is. "Depression of a child" as if that is some small thing that no one ever has experienced and cannot be extremely debilitating at times. As well as the fact that it wasn't just "depression" but also grief, trauma and loss of attachment.
Shit that can completely undo a child by human standards. But no, it's just Federation BS...SMH.