here's another quick tutorial and based on this exact top:
You will need the measurements, which means you may have to email your customer to get the measurements from her, unless you can find a detailed sizing/measurements chart for a five year old and work from there.Just always remember to add a little extra for the seams! (1/4 " or 1/2")

It's just showing the right shape just in case you don't have the pattern with you, and where the measurements will need to be placed to help you get the proper size.
If you have the measurements it'd take less than half an hour to draft the pattern, even for a very inexperienced drafter to get the basic pattern.
I hope that's clear, if you have any questions don't hesitate to ask!
Morgan
ps- in the large circle showing the armhole, there is a little "lip" going back up, it shouldn't be like that, your armhole will look more like a J-shape.