There is no need to approach J with my suggestion with the GM around. J will hopefully realize that things won't continue the way they have been. If she loses it, ask her if you are to consider this as her resignation. If she's smart, she'll back off and apologize. If her temper has taken hold, her hole will get too deep to climb out of. This is the time to talk to the GM to discuss J's dismissal. Ignore her texts or what someone tells you of her texting, it's a cowardly means of communication and needs to be ignored.