Carefully jack up the car so one rear wheel is off the ground. Put the car in gear. Have your Beautiful Assistant fully depress the clutch. You should be able to easily turn the rear wheel. If not, try it with the care in neutral. If it is free in neutral but not with the clutch depressed when the car is in gear, you have a dragging clutch.
I always, always, always, change the complete clutch when I am in there: disc, pressure plate, release bearing, pilot bearing/bush, and resurface the flywheel (if needed). Just doesn't pay to do anything less.