or she's allowed to leave her bed and delay bedtime, then she's found out that screaming her lungs out works well, eventually.
Here's what I tell parents I work with:
Pick a day, or most likely a few days and tell your neighbors to bear with you, that you're trying to get your child to go to bed and you apologize in advance for the noise. Then tell the child, "Tonight we'll read (whatever number of) stories, we'll kiss and cuddle, and then it's goodnight (or whatever your REASONABLE bedtime routine is. I'd match it to her mother's, if I could). Once we leave, you stay in your bed and go to sleep."
Of course, saying it isn't going to solve the problem, but you need to do exactly what you said. If she screams and yells, ignore her. The screaming and yelling will most likely escalate (because it's always worked in the past) but you ignore her. If she comes out of the room, silently escort her back. Don't communicate, don't negotiate, or she'll be rewarded with attention.
She will learn, eventually and probably after much screaming, yelling, and tantruming, and perhaps after many nights, that bedtime means bedtime.
The escalating screaming and yelling has a name, and it's called an extinction burst. Here's a nice explanation I found on the web
http://www.shirleychong.com/keepers/archives/bursts.txt to save me typing time:
"If someone's gained some reward every time for a particular behavior, the
behavior will persist. If suddenly the reward stops coming, it's likely
that the person or animal will not immediately give up the behavior.
Instead, they'll try it again and again, harder, faster, more emphatically.
It's a burst of activity. If the reward still doesn't come, eventually
the behavior will extinguish, or become extinct. So, the burst of behavior
before extinction of the behavior is called an "extinction burst".
Here's the example I give parents:
You're in the checkout line at the store, and your child wants a candy bar. You say okay. Nice, great, she gets it. The next time, it's close to dinner, and you say no. She starts to scream and make a scene, and you give her a candy bar to keep her quiet. SUCCESS! thinks the child. The next time, she asks, you say no, she starts to fuss, you say no, and it turns into a major screaming scene. You continue to say no, and she loses it with a tantrum that makes you cringe, sweat, and turn red. At this point, you give in, because it's really horrible and the child thinks, "Okay, eventually she'll give in."
You can see where I'm going from here. At the time when you decide to stick to your guns, you have to brace yourself for the most ear-aching, mind-numbing, headache-inducing tantrum, but it's only because the child knows what's worked in the past, and doesn't understand why it's not working anymore. The behavior escalates because she thinks that EVENTUALLY it's going to work. It's your job to stay strong through the tantrum, otherwise you're reinforcing (rewarding) the screaming, tantruming behavior.
Good luck :)