Over two days I did a few more hours of research on Jadwiga's background, digging through my memory and image searches for Polish and Lithuanian churches, and my suspicions seem to have been confirmed - it is not a real place.
Another church that is somewhat similar is St. Anne's in Vilnius, but again, many details are off, and the church has nothing to do with Jadwiga anyway (even though it was built in Lithuania, Jadwiga's husband's realm, it was constructed years after her death).
Why they did not pick an image of the spectacular castle on Wawel hill in Kraków (where Jadwiga lived, and where she is buried in the Cathedral), or the Collegium Maius building of Jagiellonian University (which Jadwiga restored, as Akademia Krakowska, the Kraków Academy), or Sukiennice (which were built before she was born, but at least she surely visited them) is beyond me.
