booby trapped

So how do you explain breast feeding to a 3 year old?? Especially one who was not breast fed...
Little Princess understood perfectly that when the baby cried she was hungry. Being a sweet generous soul, LP kindly offered to share her pasta... No Pasta? Hmmm only milk... OK but will she get ice cream if she eats all her milk? Sympathetic eyes opened wide at the idea that the baby is too little for dessert... and then it comes...
"Ok, so where is the baby's bottle?"
AH... and I am stumped.... Help! I cry to LP's mum, but she handballs it straight back to me... "Ah, right, well... you see the baby doesn't have a bottle, she drinks milk from me" I say, gesturing vaguely in the direction of my chest.
"Why does the baby drink milk out of your tummy? Is the baby's bottle in your tummy?" queries LP...logically enough...
"Hmmm well... um... babies drink milk from their mummy's boobies" I splutter, throwing caution to the wind and prompting a great deal of consternation, and the need for very close inspection of this strange phenomenon....
The next time I see Little Princess I am confronted... "Rhianon", she announces firmly, "I went and looked at the babies at my school (day care) and THEY don't drink milk from boobies...they have bottles!"
(crap!)
"Ah Yes" (thinking fast)...I suppose this is because their mummies are not there with them. They might drink from their mummies boobies when they go home from school"...
Phew, I wipe my brow as this answer satisfies for the moment.
A hidden booby-trap - I wasn't prepared for this one!