A group of maidens is called maidens. There is no word to signify a group. A maiden is a girl or young woman who is unmarried.
She was killed by some kind of mallot being struck to her head
Nancy Davis
The mothers surname before married
haylee buttmaker
water
Ed Force One
The Final Frontier (2010)
They are known as Valkyries or 'Choosers of the Slain.'
whats you name ? whats you name ? whats you name ?
All of the maidens were invited to the ball, by proclamation but not by name.
There is no specific collective noun for maidens, in which case you use a collective noun that is suitable for the situation; for example a mildness of maidens, a mob of maidens, a mayhem of maidens, etc.