Seems like the girls are attacking like it's a 2D RPG (despite not being game geeks). They are relying on their stats and skills to win, but not using their brains.
Given that it was about 8 against 3 enemies, they should have been able to tag team against each one and beat the kobolds even if they were lower lvl than the monsters. A lvl 16 losing to a lvl 6 kobold means they weren't even trying to use tactics, just brute force and lost.