Seems Rep Smith did not use the word "custody" as the legal terminology, a Government can not award custody (legally speaking), only a judge, and, in Brasil, the proper word, in regard to Family Law, is "guarda" (guard), not custody. Looks like what happened is that the federal police (and not a judge) let her go with the uncle's boyfriend (a decision that can be questioned).
Btw, a teen with 15 years old, using a fake passport, cheating authorities from the international airport of Boston, and get a plane to Brasil...I think that's very insane also.
I wonder how long US will take to demmand written authorization from both parents to a minor under 18 to travel inside and outside the country. That would prevent some of the international child abduction cases.