Tin attended Crescent Girls' School and Hwa Chong Junior College during her adolescent years. She attended the National University of Singapore to major in psychology. Prior to the formation of the 17th Young PAP Executive Committee marked by the 2011 elections, Tin was formerly assistant treasurer for Young PAP and a representative for the Ulu Pandan branch.
In the 2011 general election, Tin was selected as a candidate for the Marine Parade GRC alongside former prime minister Goh Chok Tong among others. Having been a member of the Ulu Pandan branch of the Young PAP for 7 years, she was fielded by the PAP as a candidate to attract the "unpredictable" youth vote through social networking sites. On election day, the PAP took Marine Parade GRC with 56.65% of the votes, defeating National Solidarity Party's team led by Cheo Chai Chen Goh Chok Tong admitted after the election that Tin's youth and negative image perceived by the public was a "factor" for the People's Action Party's weaker performance this election compared to their 72.9% win in 1992. On 1 June 2011, Tin announced on her Facebook account that she had resigned from her Senior Associate position in Ernst & Young, where she had worked for four years. She said the decision was made in order to focus on her responsibilities as full-time MP in her MacPherson ward and the Marine Parade GRC. Tin's selection as a candidate for Parliament in 2011 resulted in a large online backlash, especially amongst young Singaporeans. Throughout the campaign, Tin garnered negative attention due to her perceived immaturity to become an MP, and allusions were also raised as to how her husband's position had opened doors for her into politics. A widely circulated Facebook photo of Tin posing with a Kate Spade-branded gift from her husband, also led to widespread accusations online of ignorance, materialism and privilege. When asked if there was a policy she would change, she replied that there were no policy that she felt strongly against. When asked what her "greatest regret" was, she said it was not having brought her parents to Universal Studios Singapore. Some Singaporeans were concerned that as an "undeserving ," Tin had a high chance of being elected "not on own merit, but rather on the back of established MPs" since the 5-member PAP team would be voted in or rejected as a group under Singapore's Group Representative Constituency system. The public's online hostility towards Tin was so great that Goh Chok Tong defended her in the press. He said he had taken Tin in when Prime Minister Lee Hsien Loong had offered her to be fielded as a candidate in his GRC. He had accepted her as he did not think Tin was a weak candidate. He dismissed the online criticisms as "distortion" and even though "some sound bites of her which pitted her as a rather light-weight person", it was just "a superficial view". He still believed that she "would work very hard", " reach out to the young, and the not so young," that he "would like her to do more to help the old people in MacPherson," and that she would become "a good MP in due course". Nicole Seah from the National Solidarity Party team in Marine Parade GRC filed a complaint to the Elections Department on 6 May 2011, stating that Tin had violated the state-mandated cooling-off period 24 hours before polls by posting a Facebook comment on Seah crying during her walkabout. Under the Singapore Parliamentary Elections Act, canvassing on Polling Day and Cooling Off Day is prohibited and the offence carries a fine or imprisonment or both. When questioned, Tin replied that one of her administrators, Denise He, had posted the comment under her account and that He had meant to post in her own capacity from her phone, but had forgotten to log out of Tin's account. The NSP team was advised by the Elections Department to file a police report before the Elections Department could investigate. The police confirmed that a report was lodged against her. The police issued a stern warning to Tin as well as Seah, who also had a similar complaint lodged against her.
2015 general election
In the 2015 Singaporean general election, MacPherson SMC was split from Marine Parade GRC for the first time since the 2006 elections. She ran against Bernard Chen of the Workers' Party and Cheo Chai Chen of the NationalSolidarity Party. Cheo's campaign suffered a major blunder when he described Tin's new role as a mother as "her weakness" in the campaign. Facing public backlash, Cheo later claimed that this comment was meant as a joke. She received 17,227 votes, or 65.58% of the total, compared to Chen's 33.6% and Cheo's 0.82%.
