Thiel was born on 7 May 1957 in Etting, Moselle, France.^[7][8][6] She studied Medicine^[2] at the University of Strasbourg and became an intern at the Roman Catholic Diocese of Nancy in 1980.^{[citation needed]} She obtained her PhD in Medicine in 1983 from Strasbourg, followed by a PhD in Catholic Theology from the University of Metz in 1989. Her second doctoral thesis was called "Au clair obscur de la vie : pour un statut de l'embryon humain" (In the chiaroscuro of life: Status of the human embryo).^{[9][6][10][2]} This was given très honorable avec félicitations by the jury. She then began teaching ethics and bioethics at Metz and Nancy;^{[citation needed]} at Metz, she became a maître de conférence.^[10][6] While a lecturer,^{[citation needed]} she finished a diploma in European Health Policies in 1993 at the Seminary in Nancy, followed by a Habilitation in Ethics and Moral Theology at University of Strasbourg in 1998.^[6] Her habilitation thesis was called "Atouts de l'éthique systématique" (Assets of Systematic Ethics), which would inform her academic focus moving forward.^{[citation needed]}

Thiel joined the Faculty of Catholic Theology at Strasbourg in 1999, where she quickly established an interdisciplinary program in ethics.^[6][2][11] A Master's degree in ethics was also started, with her serving as Director.^[6][11] This research formed the basis for^{[citation needed]} the European Centre for Studies and Research in Ethics (CEERE), which she founded in 2005 in connection to Strasbourg's Faculty of Social Sciences.^[11][4]

Her contacts and research activities in collaboration with Yale University in the United States led Thiel to begin a summer school on interdisciplinary European Ethics in the summer of 2013. The summer school drew 41 students from 22 countries over five continents.^{[citation needed]}

Thiel has been studying sexual abuse in the Catholic Church since the 1990s. Her work as a physician and a theologian meant she was approached by sexual abuse victims; this inspired her to look more deeply at the issue.^[12][4][11] In 2017, her work led Pope Francis to appoint her a member of the Pontifical Academy for Life as part of the organisation's reform. New statues were introduced to change the lifetime membership into 5-year renewable terms, and to allow appointments to people regardless of religion.^[8] She has also advised the French Episcopal Conference for more than 20 years in its efforts to fight sexual abuse within the Church.^[12] In 2018, she published a 700-page, in-depth study on sexual abuse of minors within the Catholic Church. This book is called The Catholic Church facing sexual abuse and was published by Bayard Presse.^[2][4] Throughout her studies, she has stressed the importance of supporting and believing victims of sexual abuse, and uses their accounts in her writing.^[4]

Thiel started the Journées Internationales d'Ethique (International Symposium on Ethics) in Strasbourg in about 2008.^[6][11] She also edits the CEERE newsletter.^{[citation needed]} In addition to her books, she has published articles in several international journals.^[12] Thiel teaches and writes in English, German, and French. Though she mainly teaches in France, she has also taught in the United States, Canada, and Germany.^[12]

Throughout her work at the intersection of ethics and the Church, she has stepped forward to share her beliefs: she has criticised the Church's ban on contraceptives^[13] and classifying homosexuality as a sin,^[14] and supported vaccines to help prevent the COVID-19 pandemic.^[15] Thiel believes the Church has to be adaptive in the face of changing issues and firmly believes the Church does not intend to be "behind the times."^[16] She has also expressed support for assisted suicide, for which she was criticised by other Pontifical Academy members.^[17]

• 1992: Avancer en vie. Le troisième âge. ISBN 2220033864
• 1999: Pratiquer l'analyse éthique. Étudier un cas, examiner un texte. with X. Thévenot. ISBN 9782204062497
• 2006: Entre malheur et espoir. Annoncer le handicap, la maladie, la mort.^[6] ISBN 2868202926
• 2009: Donner, recevoir un organe. Droit, dû, devoir. ISBN 2868203868
• 2010: Quand la vie naissante se termine.^[6] ISBN 9782868204523
• 2011: Semences de vie. Trente ans d’expérience en assistance médicale à la procréation with André Clavert. ISBN 9782868204691
• 2012: Ethical Challenges of Ageing.^[23] ISBN 9781853159787
• 2013: Au nom de la dignité de l'être humain.^[23] ISBN 978-2227486263
• 2014: La santé augmentée : réaliste ou totalitaire?^[23] ISBN 9782227487444
• 2016: Souhaitable vulnérabilité?^[23] ISBN 9782868205315
• 2019: L'église catholique face aux abus sexuels sur mineurs.^[2][4] ISBN 9782227496033
• 2022: Abus sexuels – Ecouter, enquêter, prévenir with Anne Danion-Grilliat and Frederic Trautmann. ISBN 9782868207623