Hair changing colors

I had very pretty blonde hair as a child, but as i grew it turned dark and i wish i had my blonde back naturally without having to dye it.

My daughter was born with my same pretty blonde hair and when she turned 3 her hair started turning darker and now is almost the color as mine now, I miss the pretty blonde and I want it back!!!

How can I naturally get her blonde back ??

I read that hair turns due to lack of melanin ... is there a special shampoo or vitamin we can take to boost out melanin??