Hey there,
Aww its tricky when they start coming out with their bag of tricks :? isnt it ...
My little one has done this to me more than once, and like the rest of the parents on here said, I also stick to injecting after food, however as his dinner takes ages to be eaten by him sometimes the diabetes nurse has asked to inject 1unit of novorapid at the beginning of the meal, and the rest of whatever insulin hes meant to have with his meal at the end of it...
However if your child eats it up in reasonable timing, inject straight after she finishes her meal, hypos are quite difficult to treat sometimes depending on how low they are, and to the best way to avoid in regards to your case would probably be to inject straight after her meal as opposed to before as kiddies are very unpredictable, and with your DLA form get your diabetes nurse to do it for you as they know what to write in regards to medication, injecting etc , or atleast give you a hand.
Best of Luck