You can't set the faction's for the player twice, PedSetFaction(Player2,15)
PedGuardPed(Player2,Gplayer)
To make ped's guard you, you have to set the ped's focus without the ped being a bodyguard or ally. Just spawn the health bar and Allyblip then that ped will react like a BodyGuard but you will be able to set functions for that ped without interruption.
Learned this from Busting In Part 1 it is similiar to how they make Zoe appear to be a bodyguard but she is just a normal free roam ped set to be a bodyguard. I managed to get the bodyguard's for the Zombie Mod to work in a similiar way.