It wasn't law when she took her oath therefore she didn't break her oath.
Yes, she certainly did break that oath, because she took an oath to uphold the Constitution, & the Constitution is a living document, which means that anytime it is amended or interpreted for the inclusion or exclusion of any specific person, or idea- then she still must follow it. & she must do so without religious bias.
A Living Document
The creators of the U.S. Constitution knew that the document might have to be changed in the future. They even included the rules for making changes right in the Constitution. In all, the Constitution has been amended 27 times. This time line highlights some of the most important amendments.
1865.......The 13th Amendment outlaws slavery in the U.S.
1868.......The 14th Amendment says that the Bill of Rights protects all citizens equally. 1870.......The 15th Amendment says that a person cannot be denied the right to vote because of race.
1920.......The 19th Amendment gives women the right to vote.
1951........The 22nd Amendment limits the President to two four-year terms in office
1967.......The 25th Amendment says that the President can appoint a new Vice President (with the approval of Congress) if the Vice President dies or leaves office.
1971........The 26th Amendment lowers the voting age to 18.
https://constitutionday.aclu.org/docs/alivingdocument.pdf
Why is the Constitution called a living document (amendments process)?
The Constitution is referred to as a living document because it is open to constant change whether by ratifying the Constitution with a new amendment or by repealing an existing amendment. Consequently, as time goes on and new issues and concerns arise, the Constitution can be changed to meet the demands of the present and future.
Additionally, the Constitution is open to constant interpretation by the Supreme Court. Hence, even though abortion and automatic weapons were not issues during the Constitution's conception over 200 years ago, the Constitution can be interpreted to protect or restrict rights on a variety of issues.
Why is the Constitution called a living document
For example, at one point, the Court ruled that separate institutions for black and white citizens were perfectly legal and constitutional, as long as the institutions were equal in power and efficacy — the "separate but equal" doctrine. In this century, the Supreme Court turned this doctrine on its ear by declaring that separate cannot mean equal, and segregation was unconstitutional.
http://www.usconstitution.net/constfaq_q93.htmlhttp://www.usconstitution.net/constfaq_q93.htm
http://www.law.harvard.edu/students/orgs/jlpp/Vol29_No2_Rehnquist.pdf