Pull-ups suck, I think they just confuse children. We use them for out and about at the moment with Yasin but as soon as we run out it's undies because when he has them on he doesn't bother telling me he needs to loo or the potty.
I would just let her keep doing what she's doing and soon enough by accident something is bound to happen when she's on the loo. At that point you can make a bit of a fuss and so that she understands that she achieved something.
Is she pretty regular in her habits? If she always has a poo after breakfast or pees after her nap you could pop her on the loo at those times to increase the chances of catching her in the act.
If you knit maybe you could make some TT pants with long legs and a open bottom.