When I was a child (6-7 yrs old) my mother told me about 'mating'. I remember seeing two wasps on top of each other and asked what they were doing. She said 'they are mating and that this is how they make more wasps'. She said that all bugs, humans and animals do this to have babies. Somehow this was enough for me. A year later I saw two dogs together and I figured out that they were also 'mating'.
When it comes to teaching a girl about puberty, I believe my mother just told me that it was about 'turning into a woman'. When you get a little older, you can expect that your hips will grow, breasts will develop, you will start using deoderant, start shaving legs, and a period will start. (I already knew a little about a period, because I knew my mother had one) She just explained that this is how a little girl turns into a woman. As a little girl in elementary school, I was excited about this because someday I wanted to turn into a woman!
I hope this helps! Good luck!