While details of Onyango's asylum request are not being disclosed, her case was at least compelling enough to convince Shapiro in December 2008 to take the unusual step of reopening the matter and issuing a stay on her deportation.
Experts speculate that Onyango could be claiming that her relationship to Obama makes her a target of Kenya's political tribal factions fearing her perceived influence, or of Islamic extremist groups seeking to inflict harm on the U.S. president's family.

White House Claims No Involvement With Onyango, Hearing

President Obama's Aunt Zeituni Onyango Fights Deportation - ABC News