Facts
[B.A.] and [A.A.] (both German nationals) had married on 1 December 2006 in [U.] (Germany). They are the parents of [C.A.] (born 15 May 2005). Since the beginning of June 2010, the spouses have been living separately. By judgment of 6 December 2011, the Amtsgericht Konstanz (Germany) dissolved the marriage. In addition to the divorce, this judgment only regulated the internal division of the German Pension Insurance and the procedural costs.
Based on the authorization to sue granted by the Friedensrichteramt Kreuzlingen on 3 November 2015, [C.A.] , represented by his father, filed a maintenance claim against his mother [A.A.] at the Bezirksgericht Kreuzlingen on 16/17 November 2015. He requested that [A.A.] be ordered to pay monthly payments of CHF 437.-- from July 2015 until the completion of his initial training, but at least until his 16th birthday. He also claimed CHF 9'177.-- in maintenance for the last 21 months since moving to Switzerland, plus 5% interest from the date the decision becomes legally binding.
Subsequently, the parties agreed to continue the proceedings as a case concerning the modification or supplementation of the divorce judgment, with [B.A.] as the plaintiff. By decision of 19 September 2016, the Bezirksgericht supplemented the divorce judgment of the Amtsgericht Konstanz and obliged [A.A.] to pay monthly advance maintenance contributions of CHF 250.-- plus any child allowances from 1 January 2017 and of CHF 300.-- from 1 June 2019 for [C.A.] 's maintenance.
Considerations
The Obergericht of the Canton of Thurgau confirmed the first-instance decision. It found that the appellant [A.A.] was only formally employed full-time throughout the year at the "[D.] " of her life partner. According to her own statements, she was only employed 100% during the main season from April to September/October; for the rest of the time, there was practically no work due to seasonal conditions. From this, the Obergericht concluded that the appellant's workload on an annual average was little more than fifty percent. It was not understandable why the appellant should not be able to pursue actual full-time employment under the given circumstances. In order to pay an appropriate maintenance for her son, a change of job was "not only reasonable, but even an obligation" for her.
To determine the appellant's hypothetical income, the Obergericht referred to the Vierteljährliche Verdiensterhebung (VVE) conducted in Germany. For the federal state of Baden-Württemberg, a minimum income…