Missouri high school student Kaylee Gain and the fellow student involved in the attack that put Gain into a coma exchanged insulting text messages in the weeks before their March 8 fight, her father has revealed. During the fight, Maurnice DeClue was shown on video pounding Gain’s head into the pavement. The violence of the attack has led to calls for DeClue, 15, to be charged as an adult. DeClue’s family says she should be charged as a juvenile. Clinton Gain, 41, said the insults flew back and forth for weeks, according to the New York Post. On the day before Gain, 16, was pounded into a coma…