I know with my ds1, sometimes he needs the extra push to try something (as he did with pooping in the potty) and after he sees the first time that it's not as hard as he thought it would be, he's willing to try it again. So for him, while we had a few days of some naked time and practicing the potty stuff, that meant physically putting him on the potty when we noticed he needed to poop (and being very encouraging about it).
Another idea I have is to try to provide a different toilet seat/potty/place to poop. If you're using a potty, try putting a special seat on the toilet and provide a stool to put feet on. We have installed a great child/adult combo seat on our toilets, so it's like the real thing, just smaller. Something like that might encourage her to try it? Or, have naked time and if she needs to poop maybe put a diaper on the floor somewhere or right over the potty so she can try out pooping without a diaper actually on?