Princess Margaretha didn’t wear a tiara, she wore a traditional Swedish nuptial crown called a brudkrona from Gärdslösa Church where she was married.  I’m not Swedish so this is just want I’ve gleaned from the internet but apparently the church or parish owns the crown and it is lent to all of the brides that get married in that church.  There are nuptial crown traditions in other countries and cultures but I really like the Swedish one because they are owned by the church and can be used by any bride as opposed to the ones that are owned by royal and noble families.  It just seems very Swedish to me.  This is Princess Margaretha wearing the crown from Gärdslösa Church.

And here are a few others

Täby Church in Uppland

Boxholm in Östergötland

Saint Olaf’s Chapel in Närke

Malmbäck Church in Jönköping

Backen Church in Västerbotten

Rättvik Church in Dalarna

The Nordic Museum in Stockholm also has a large collection of them which you can view online here along with their collection of photos of the nuptial crowns being worn by brides.  If someone from Sweden knows more about them particularly if they are still worn often please let me know.