Okay...so you know when you're playing CandyLand and there's these pits you can get stuck in, like the Gooey Gumdrop Pit and Molasses Swamp? Well, when potty training, you are inevitably going to get stuck in the Bedtime Potty Pit. This is when your child realizes that if she cried Pee! she can stall her bedtime. If she cries Pee! a lot, she can stall her bedtime for HOOOOURS. And if she cries Poop...oh boy...endless stories on the potty.
This is the ULTIMATE in the bedtime stall. You can kiss "one more story" goodbye. This is a whole new ballgame.
The reason this is so effective a stall is because in the beginning you are unsure (I tell ya...toddlers can smell weakness)...so you feel you have to honor the asking. What if she asks and you say no and she pees in bed (whether or not she's got a diaper on)? You don't know if she's playing with you or not, so you can't push this issue.
DO NOT LET THE BEDTIME POTTY PIT GET OUT OF HAND. Your child simply can not afford to lose sleep. Not really ever, but particularly while potty training. She's learning a lot and sleep helps assimilate all that information. But also, an overtired kid the next day is more prone to accidents and resistance...to the potty and to life in general.
Build in the stall. So let's say, bedtime is 7pm. Normally you start your routine at 6:30. But with the bedtime stall she's actually going to sleep at 8. What was taking you a half hour, now takes an hour and a half. BUILD IN THE EXTRA HOUR. Or at least a portion of it. Start your routine at 6 or 5:45. Part of what drives the cuckoo in this stall is that we know we are on the clock. Every precious minute we're losing we can see in bad behavior tomorrow morning. Us, getting tense, will NEVER help the BPP. When you build in a cushion of time, you can be more relaxed and thus, more effective.
If this seems RIDICULOUSLY early...do it anyway...it's completely temporary.
Give your child x amount of times to try. I suggest 3 times, as we universally run on a 3 strikes you're out philosophy, but any (low) number will work. Make it clear to her that you are giving her 3x. Each time she tries, tell her how many times she has left. Really, if she HAS TO GO PEE...it will happen in 3 tries. If she cries poop, first look back on the day. If she's had her normal amount of poop, chances are she doesn't have to go. But if you want to try, either set a timer or time it through something like stories. "Okay, we'll sit for 2 stories. If your poop doesn't come, we'll try in the morning."
Then FOLLOW THROUGH. Most parents still use night diapers in the beginning. It's better that she pees in the diaper than stays up half the night "trying" to pee. I've seen it happen where the parent doesn't want to set the boundary. The child suffers, trust me. If the bedtime gets too stalled, your child will enter a different circadian rhythm and be up for even longer. Not good.
Usually, just doing this little routine nips it in the bud. Like with most things, this is about setting a boundary and following though. If you don't set the boundary, she will take it too far. It's the nature of toddlers (through teenage years, I think).
Over tired is the fast way to derail potty training.
And your sanity. Just about everything, really.