How can I stop my cat from crying as soon as the sun comes up?

We have 3 cats. One of them has started to cry in the mornings. She starts at sunrise (which is 5:00 am now) and continues until one of us gets up. She has access to outdoors via a cat door on our balcony and I'm afraid the neighbours are being disturbed too. Soon we will be on holiday and I worry she will keep this up while we are gone (we have a cat sitter but only twice a day). Maybe she is hungry but we can't leave food out for her because one of our other cats is diabetic and on a strict diet.