Citzenship 

1 - My understanding is she was born in the UK but from an Irish father and mother from British occupied country (Northern Ireland). From what I read she would take after her mothers heritage and is actuall an Irish citizen (Irish passport and all) and recognized as a UK citizen granting her dual status with both of those countries. Seems pretty common from what I have read.

2 - She applied and received her US Citzenship status in the early to mid 90's. Seems pretty common that people, especially in politic, carry two passports and maintain dual citzenship status. Especially if their parents are from Ireland.

I think that it should be noted that she was born in London but retained her Irish identity and was honored to receive her US citzenship status in the early 90's and is one of the many that enjoys a dual citzenship status.