It must be extremely frustrating IRT the inconsistency with her routine

Sometimes it can take weeks like aussienic says
it is perfectly normal to take 2 steps forward and one back when TT
I found this to be so true! Angus would proudly poo on the toilet one day and the next he'd try and stop it with his heels up his bum and we'd be back to square one almost. I found that star charts helped a great deal. One star per poo on the toilet and then when she gets three give her a freddo frog.