Either could win the fight, well like I lean more to the Flame Princess by logic but the ice queen has powers that are not to be taken lightly, if anyone saw "ignition point" you will notice that the ice could be lethal to the fire people because her cousins tried to kill to King flame with just a few ice cubes D: now imagine a big blizzard on the poor princess flame D:, to finish in the picture may be the end of that fight with a draw , with that claw traversing the chest of the princess and the great fist of fire of the flame princess alike traversing the ice queen
Also... GO ICE QUEEN!!!!!!!!!!
DAYUM!!!!!!!