I potty trained in the daycare setting for years.
I have 2 suggestions for you:
1. Put a TV tray in the bathroom for her to have a surface to do activities in the bathroom. It can help her to relax if she is not just "thinking about it". Have coloring books and crayons handy (also, puzzles, books, etc. that can be done on the small table). This way she may sit longer too. Set a timer for about 15 or 20 minutes and tell her that when the timer goes off she can get up, but she can "play" there until then. Take the timer out of her sight so she is not compelled to look at it (if it doesn't beep when you push the buttons, you may want to add a couple of minutes when she isn't looking if she is sitting well).
2. Do you have a potty training doll?
I used to use it to show the kids how to poop. Get some tootsie rolls (without her knowing you have them or it will ruin it since she is old enough to understand things that a younger child might not). Hold the doll over the toilet. Without your daughter realizing it, drop a few tootsie rolls into the toilet behind the doll. Get excited when you hear it drop into the water. Get her to look and see that the doll has gone poop.
It may or may not work with her at this age, but it is definately worth a try.
I know this may sound "gross", but since kids learn by example you may even want to allow her to be in the room when you go (once or twice) maybe while she is in the bath (so she won't leave the room). Just a thought. I had my husband show our boys how to pee, but it may work for poop too. Shrug.
Good luck!
P. <><