During the time Frank had the war gods bickering in his head, the same thing was happening to all his children.
The children of Mars all had splitting headaches and impulsive urges to kill all the Greeks. The rest of the Romans were left trying to figure out a solution for a problem they didn't know the cause of.
Meanwhile, the children of Ares were the laughing stock of Camp Half Blood. They were becoming increasingly more agitated with each passing day. But their headaches came in waves, they could be fine one second, and the next, be lying on the ground moaning, or attempting to tango with the person nearest them.
Clarisse was the only one who didn't seem to be negatively affected by this. She seemed to get angry really easily, more so than usual, but other than that, didn't have any of the side effects like the rest of her siblings. Being the only daughter of the war god, Greek or Roman, the god's first instinct (although he didn't realize it himself) was to protect her.