D.Z.
N.,
Don't sweat it. Let her keep practicing, try to address any anxiety she is having, and know that this too shall pass. Sounds like she is doing great, since it has only been two weeks. She's still pretty young, and it can be a hard transition.
I don't think any form of laxative is appropriate in this situation. Your description makes it sound like she is just nervous, and that will pass. If you give her laxatives, she might lose bowel control, and that will be very scary and will complicate the issue. Sounds like she already has the urgency and need to go, so I think it will come along just fine. Keep encouraging her and try not to make a big deal out of it.
You're both doing great!