Maybe you could get a puberty book aimed at younger/tween girls & read it together. Have pads,tampons, etc where she can access them if needed & explain to her it's something that every girl goes through.
Maybe you could also get her a body spray and get her in the habbit of putting it on everyday for when she does start to need deodourant, you could also go shopping together for crop tops/training bras

Hope that helps, good luck