GF drove the jeep for an hour with parking brake on and now fluid leaking from driver rear tire....is this just something to refill? Or do I need to be concerned?

 

The parking brake is cable actuated, not hydraulic. It sounds like her mistake just brought your attention to an issue. You've got to figure out why the fluid is leaking- if it's coming from the rear tire (e.g.not the caliper) then that would be differential fluid. Pull the rotor off and take a look then take some pictures.