Lovely! That tiara is an old acquaintance indeed. It has been worn by Fürstin Manni, e. g. at the pre-wedding of her daughter Theresa. Then Princess Theresa wore it as her wedding tiara, as did Princess Gabriela, nee Countess von Schönburg-Waldenburg. I also think that Princess Elisabeth wore it, while I haven't seen a wedding pic of the eldest daughter Princess Marie Yvonne. I think it was also worn by Princess Elisabeth's daughter Isabelle Baroness von Senden (a first cousin of the current bride) in 2001. So yes, it has a tradition as wedding tiara in the family.
The pearl and diamond tiara that has been worn Princess Priscilla, Countess Philippa Spannocchi and Alana Bunte seems to come from Princess Gabriella's family, since seems that it has been worn by her mother Countess Helene von Schönborn-Wiesentheid, nee Thurn und Taxis.
Therefore my conclusion is: the floral tiara originates from the Sayn family and therefore Manni wore it herself and also loaned it to her female-line granddaughter Isabelle von Senden.
The pearl and diamond tiara is the either a Thurn und Taxis piece or a Schönburg-Waldenburg heirloom and is only worn by Gabriella and her daughters and daughters-in-law. So it would have been the other option for Princess Sofia, but she chose granny's tiara.