Born in Hachenburg, she was the eldest child of Ernest, Count of Sayn-Wittgenstein-Sayn and Countess Louise Juliane of Erbach.
In his will, Count Ernest left his domains to his only son Louis, under the regency of his mother Louise Juliane during his minority.
A violent dispute over his inheritance erupted between the Dowager Countess and the three half-brothers of her late husband (sons of Count William III and his second wife Anna Ottilie of Nassau-Weilburg), who claimed the succession of the whole County.
[2] After two months, one of them, Count Louis Albert of Sayn-Wittgenstein-Neumagen, finally forced Louise Juliane to surrender the County to him and his brothers.
One year later (1652), Louise Juliane finally handed over the County of Sayn to her daughters, who was divided in two parts: Sayn-Wittgenstein-Sayn-Hachenburg (for Ernestine) and Sayn-Wittgenstein-Sayn-Altenkirchen (for Johannetta, who was at that time Dowager Landgravine of Hesse-Braubach).