*hugs hugs hugs* I think tough love super nanny style is required.
Can bub go to someone's house for a few nights or possibly bub & hubby? And then you & 4yo stay home. Let her yell but DON'T go in there.
If she's smiling at you & saying hi, it's not a night terror. She will probably EVENTUALLY get tired from yelling and fall asleep OR come looking for you, at which point pick her up & carry her back to bed.
Don't know how practical this is & will probably be 3 nights from hell but it might break the habit.
Or schdule an appointment with a Paed/psyc