Royal Caribbean usually has casual gatherings for older teens and also for younger single people where they can socialize and find new friends. They will have information about this in the Cruise Compass on embarkation day, or you can simply contact the youth staff and ask them.
The night clubs allow 18 year olds, I think. If they are young ladies, I don't think meeting people will be a problem. They might need a large stick, however!
Looking for our next cruise!
Sovereign of the Seas (Sept 2002)
Enchantment of the Seas (Sept 2003)
Monarch of the Seas (August 2009)
Monarch of the Seas (April 2011)
Enchantment of the Seas- Port Canaveral (May 2013)
Enchantment of the Seas - (April 2014)
Enchantment of the Seas - (January 2015) YES AGAIN!