The 'virgins' are those not defiled with the harlot daughters of Babylon.

................They have come out of Babylon.

Friendship and conformity with the world is considered spiritual adultery.

...........................James 4:4
" Ye adulterers and adulteresses, know ye not that the friendship of the world is enmity with God? whosoever therefore will be a friend of the world is the enemy of God."