But Why?

I can't even explain how crazy this summer has been. It was supposed to be a nice, relaxing summer with lots of time to sleep in and chill out. It has not been that way in the slightest. Without going into too many details, I've ended up staying with my brother and sister-in-law for an extended period of time to care for their two children, who are turning 1 and 3 years old this summer. My three year old niece is quite intelligent, and curious about everything. Since the very beginning, I have never lied to M about my diabetes or my pump. When she asked "What's that?" and pointed to my pump, I would always reply that it was Aunt Jen's pump. She never asked beyond that. Until now. She has reached the "why" stage. I scrambled to answer when she pressed about why Aunt Jen wears a pump, and why I need medicine. So I've come to the fine folks of the DOC to help. What do you tell the young children in your life about your diabetes and diabetic supplies? Does anyone know about any good books that would help explain? A book that has a pump in it would be very helpful, since that is what she is asking questions about.
Thanks in advance! I have a lot of things to post about, so you should be seeing me a little more often!