My daughter is 3 and she has to have things a certain way too. Apparently we did a great job establishing a sleep routine for her because heaven help you if you try to deviate from it or cut corners. She needs 2 stories, her 2 teddy bears and to be tucked in with 3 blankets - the same 3 blankets in the same order. She needs both her humidifier and her CD player with lullaby music on.
So I would say it is normal - it's their way of being in control and taking comfort in routine when so much of their day and their life is not in their control and often can seem very random.
I would just give her the things she needs right off the bat and make sure nothing is out of place before you leave the room, just so she does not have a reason to keep calling you back.