"I've never met a kid who enjoyed having poop in their underwear. I know several who don't care about a poopy diaper though.
Get a pack of some super special character panties that she really loves, and get a pack of some super boring white panties. If she poops in her character panties, have her throw them away. She needs to know it's just not acceptable to poop in your pants. Have her put on some white panties, and she can try with some new character panties after nap, dinner, whatever. This was a really good motivator for my kids."
Just had to reply to this part of your post. There are plenty of kids who don't give a crap (no pun intended) whether they poop in underwear or in a diaper - my DD included. We have special character panties that my DD loves that she can wear as a reward for pooping in the potty. Glad that helped with your kids, and wish it worked for my DD, but that hasn't been the case, unfortunately.