I just don’t get people…

Your sister may have broken her elbow.  She waited to see the doctor, and fluid started accumulating.  Yet, because you also need to see the doctor for something minor, she drives you 30 miles to your (mutual) doctor (to save you from driving).  So… how do you express your gratitude?  By griping her out when she needs to go get an X-ray after seeing the doctor.  (Cl)assy…