Just what sntrym says. For your daughter you want a truck that is not going to strand her somewhere. The rad cap is cheap and so is the T'stat. I'd change both, just for insurance. If the temp gauge still reads high, borrow an infrared thermometer, and shoot the area by the thermostat housing. If it is still hot, well, it is possible that the rad is partially blocked, or the water pump impeller is not doing the job, again, not terribly expensive to fix either of theses.
If still not right, a combustion gas test, as suggested earlier in this thread is the next step.
Good luck, and keep us posted.