P.B.
It is very important that along with the fibers she gets enough water through drinking. Infact just fibers have the opposite effect than expected: the make hard stools, dry and difficult to pass. I think she feels the need to go because the fibers "scratch" her bowel giving her the impression that it's that time, but then the poop is too hard and scaly to make a whole, moist piece (sorry for the description, very disgusting, I know), so it comes out broken up just like you say. Too much fiber and too few water is often the cause of IBM in the future adult life too, so my advice (on personal experience) is that she drinks lots of water and real fruit smoothies (pear, kiwi, strawberry and banana for example) to have her stool soft and easy to pass. That will make it more comfortable to go and she will make friends with the potty more easily. Good luck!!!