take her to a sleep specialist to see if she has sleep apnea....it happens in kids....allergy medicine can make a kid "hyper" and then they won't sleep.
Instead of just asking the Drs - FORCE them to find out what's wrong - at 4 she should be sleeping AT LEAST 8 hours a night....they are giving you a cop out instead of trying to figure out what's wrong.
have her tested for any sleep disorder...I can't believe the dr's have just given you some lame excuse - this has been going on since she was born!! COME ON!!! ENOUGH ALREADY!!! You are your daughter advocate. YOU take on the drs to figure out why she won't sleep the night through.
If it's habit - it NEEDS to be changed and NOT encouraged. IF she wakes up in the middle of the night - she MAY NOT wake up anyone else. If it's an emergency - yes. But just because she woke up? NO FRICKING WAY!!!
She might have too much stimulation. Too much light. Too much noise. Try taking out the humidifier - it could be her room is too wet/damp to sleep. Get a thermometer/barometer to find out what her room is like - it should NOT have any more than 38% humidity - if it does - it's just too much.,..causes mold, irritation, etc.
Make sure the routine is the same - bath, brush, book, bed. Low light, low noise and keep this the same. Routines start after one week of doing them and a habit after a month. If she's been allowed to do this - wake you and every one else up - then it's not habit and the only way to stop it is to create a new habit.
I STRONGLY urge you to have her tested and DO NOT LET THE DOCTORS GIVE YOU COP OUTS.