Possible that you have 2 separate unrelated problems. The overheating could have been the radiator needed water, which apparently she fixed. But now, make sure the radiator hoses are not plugged by taking the radiator cap off the cold engine, then start the car, and watch the water inside the radiator to see if it is moving around. After a couple minutes, stick your finger in the water to see if it is heating up. If so, it's circulating ok. If not, either plugged hose or bad water pump. But now the back wheel locking up, check to see if the emergency brake is stuck, or possible the rear pads came apart and bound up the wheel, or could possibly be the wheel bearings.