The advice I received from family, and what eventually worked - do not buy more pull-ups/diapers. Make her wear only "big girl panties". We did have quite a few accidents (luckily we have mostly hardwood floors though) but she's gotten the idea now, and uses the potty almost every time. She too took an interest at about 18 months, and just turned three in May. The accidents are fewer and farther between now, and we've been able to go back to overnight diapers without her wanting a pull-up all the time. Heck, she currently prefers nudity! But on that note, she is getting better overnight and I think we're almost all the way done with diapers, period! It feels like it was easier to train the boy....

Hope that helps!

~Julia