User blog comment:B214/General Discussion/@comment-24098614-20170717210130/@comment-3435913-20170717214503

Her sword was taken to heaven so that the pieces of Exaclibur would be forged into a sheath to control the sword's untamable nature (the reason why it's chained in another dimension). The sheath stays on the blade during battles, but the sword fragments can form an individual sword from it's previous pieces, and later when all seven are reforged together, they can be reformed into True Exclaibur. Since the sheath can be seperated from Durandal, this is how she can weild both swords.