Eithne Uathach, Leinster - Inconsistencies Addressed

I believe the inclusion of "Leinster" as her last name refers to her father being the King of Leinster.

But the main question is whether or not she was the wife of Óengus mac Meicc Eircc. There was another Óengus who lived about this time, Óengus mac Nad Froích, who was the King of Munster. He is a different person than Óengus mac Meicc Eircc of the Ó Bairrche (Uí Bairrche) family.

Since many of the children listed for Eithne are "of Munster" they are likely the children of the other Óengus, meaning that Eithne was not actually the wife of Óengus mac Meicc Eircc, but of Óengus mac Nad Froích. That would clear up the confusion about her children's different surnames.