Shanks was born in Dannevirke in 1969, and attended St Matthews Collegiate for Girls in Masterton and Dannevirke High School. She graduated with a Bachelor of Business Studies from Massey University.
Shanks' father, Graeme Hislop, twice stood against National Prime Minister Keith Holyoake as a Social Credit candidate, in 1975 and in the 1977 by-election.
Prior to entering politics, Shanks worked as a self-employed accountant. She had previously worked as a project accountant for the Westpac Banking Corporation, in retail client services for Newton Investment Management in the United Kingdom, and as a senior auditor for Audit New Zealand. Shanks has three children.
Shanks joined the New Zealand National Party in 2001 as a member of the Karori branch and was a member of the party's executive committee for the Wellington Central electorate until 2004, when she joined the Ohariu-Belmont branch.See Ohariu-Belmont electorate results in the 2005 New Zealand general election
Shanks sought the National party's nomination as their candidate for the Ohariu-Belmont electorate at the 2005 general election in 2004. She was one of two final challengers, along with Simon Wright. Shanks was eventually confirmed by National Party Ohariu-Belmont electorate chairman Tony Heyward.
Shanks was placed 46th on the National party's list for the 2005 election. In the electorate vote, she placed third behind the incumbent MP, United Future leader Peter Dunne and Labour's Charles Chauvel, with Shanks gaining 7,329 votes, a gain of 2% from the 2002 result for National candidate Dale Stevens. However, National's party vote within the electorate increased by nearly 19% and exceeded that of Labour (although they had also improved slightly on their 2002 result).
The initial results for the election on 17 September 2005 (election night) would have seen Shanks elected as a list MP; but the official count including special votes resulted in Shanks not going into Parliament on the list. The number of National list seats was reduced by one when the Māori Party share of the party vote rose above 2% and they were entitled to three not two seats from the party vote. They had won four electorate seats so the number of overhang seats in Parliament reduced from two to one. As National had the 120th seat allocated under the party vote, National lost one list seat that they appeared to have on election night. However Shanks' list position meant that if any National list MP resigned, Shanks would become the next National MP. This happened when former party leader Don Brash resigned on 7 February 2007.
Shanks became her party's Associate Spokeswoman for Commerce and Associate Spokeswoman for Economic Development, as well as a member of the Social Services Select Committee, which she held for the remainder of the 48th Parliament.See Ōhariu electorate results in the 2008 New Zealand general election
Shanks, along with Dunne and Chauvel, contested the same seat again in 2008, within the newly named Ōhariu electorate (with modified boundaries from the former Ohariu-Belmont electorate). Shanks placed third again in the election, although National received 46.3% of the party vote in the electorate.
Shanks was again placed 46th on the party's list for the 2008 general election, and her party's result meant that she returned to Parliament. She was not offered a ministerial role as part of the new National Government.
In 2013, Shanks was co-chairperson of the Regulations Review Select Committee, a member of the Māori Affairs Select Committee and also a member of the Justice and Electoral Select Committee in the 50th Parliament.
Shanks had an office in Johnsonville, Wellington, which was officially opened in September 2009 with Prime Minister John Key in attendance.
In April 2011, Shanks delivered a speech praising the pending anti-file-sharing copyright bill known as "The Copyright (Infringing File Sharing) Amendment Bill". Opponents of the controversial bill quickly responded on Twitter and created YouTube parodies comparing Shanks' speech to a contestant's bumbling speech during the 2007 Miss Teen USA beauty pageant. The bill, which aims to prevent Internet piracy, passed overwhelmingly with a 111 to 11 vote.
Shanks originally planned to step down at the 2014 election, but instead retired at the end of 2013 to become Chief Executive of the New Zealand Funeral Directors Association. The resignation became effective on 21 January 2014, and Shanks was succeeded as a list MP by Jo Hayes.