R. - we had the same problem with my son. Pooping in the potty is scary!! What we did is we had a long talk and told him anytime he had to go poop, to ask for a pullup. He did - and then would go in the other room, poop, and then we'd take it right off and go back to underwear. The pressure surrounding going in the potty was very stressful to his digestive tract and was causing a lot of problems. The solution of the pullup really worked & then helped him really understand his body's own signals for pooping.
This was what we did for approx 2-3 months, then we approached the potty - he got candy for going in the actual potty, but not in his pullup. We still did a no-pressure thing - he got to choose how to go, but eventually the candy won out.
So maybe my method would work for you. If she is in the habit of going at the same time each day, you can start by putting her i a pullup about a half hour before & just not even saying anything.
Try not to let her feel bad about going in the pullup. She's still really young! It's okay for her not to get it down yet. Allow her to progress through this at her pace, not yours, and just give her the tools and encouragement to become fully potty trained. She'll get there, I promise. Good luck! S.