she sounds intj too.....
my intj son (the eldest of my kids) was relentless about finding out about how babies were made. He was only 5 at the time, so I could see that an intj could find out about santa at 6.......
intj son: how are babies made?
me: mommy and daddy love each other so much we make a baby
intj son: but HOW do you make a baby?
me: well, we snuggle and it happens
intj son: how?
me: when daddy and mommy snuggle it just can happen
intj son: but how?
me (exasperated by this time): daddy's sperm and my egg join together
intj son: but how do they join?
me: there is a place inside me where it just happens
intj son (relentless!): but how does the sperm get to the egg?
me (resigned at this point): daddy's penis goes in my vagina and the sperm meets the egg.
silence.........
intj son: oh.
end of discussion. no other kids of mine has found out about the miracle of life at so young an age. gotta love intjs!