This is Dr. David
your friends explanation is one answer.
also your pancreas could also be producing more insulin at this point. this can happen if you have lost weight recently
after a meal, it is normal for your pancreas to produce natural insulin.
if your pancreas is producing more insulin now for some reason, this can cause you to have drops in your glucose levels after meals.
this is rare for the pancreas to start producing more insulin, but it can happen.
you might need to see an endocrinologist and get your insulin levels checked after meals without insulin injections
and you might need to back off on your insulin dose if this continues.
let me know if you have other questions.