Being that she is holding in her bowel movement, it probably is getting hard.
I have a good friend that is a RN and she told me that if we eat the "white" (which is virtually tasteless) that it softens the stool. The white from one orange does do the trick.
I would try to get her stool softer and after she eats breakfast, I would set her on the potty for a while. I would give her a toy that she likes to make the time a bite more tolerable and help the time to pass on a more pleasant note.
When she pees or even pooped a little bite try praising her and tell her what a big girl she is. This worked with a niece of mine to the point that she didn't want to flush the toilet so she could show someone else :)
About Me: I'm 60, been married for 38 years and have two grown sons.