I didn't change her. She usually sleeps 30 minutes max at nap time (lucky me!) so I didn't want to risk it... She doesn't have a problem with diaper rash - hardly ever has had it (knock on wood) so I felt okay there.
Of course when she woke up 25 or so minutes later - she had pooped more and her pants were wet. *sigh* So I should've just changed her - her cute outfit would've been saved and she probably would've slept for 25 minutes later anyway. Ah well....I guess each situation is different. Welcome to motherhood. :)