Following the Nazi pillaging of her family’s treasures and their theft by a German youth, a destitute Dutch girl traces a mysterious red velvet pouch to Australia where, pursued by German agents, she recovers her family diamonds and falls for the thief’s grandson.

The victim of a Nazi atrocity, a destitute Dutch girl traces a mysterious velvet pouch to a German woman in Australia where she seduces the son to retrieve the diamonds of her birthright.

There's still zero conflict in this version of the story. The jewels weren't stolen from her, but her ancestors. In story terms, this is pretty problematic. This is what happens in your story:

She goes to an archive and finds out someone in Australia had something to do with the theft. (Where did this pouch come from? Does she have it to start with or get it at the archives? Or does she not even have it, but just know about it?)

She goes to Australia and is led to the diamonds.

Everything works out.

That's not compelling AT ALL because there is no conflict. Nobody is trying to stop her. It's not even a DIFFICULT mystery to solve, because currently she solves it in the opening act! And there doesn't seem to be anything at stake other than some diamonds that SHE NEVER HAD, and has lived her whole life without to this point ...

Decades after the Nazi pillaging of her family's treasures a destitute Dutch girl visits a new records facility and traces a mysterious velvet pouch to the thief's sister in Australia where she seduces the son who leads her to family diamonds and the affluence to survive with him.