This passage in the NIV, verses 13 through 15 shed some light on who the virgins are. It makes sense in that the Bride is not 10 people nor is she "split" in half!
"All glorious is the princess within her chamber;
Her gown is interwoven with gold.
In embroidered garments she is led to the king;
her virgin companions follow her-
those brought to be with her.
Led in joy and gladness,
they enter the palace of the king."

L.Lee