Hi Leigh!
She is old enough to try ricemilk or any other type of grain milk, but I would wait until she is 1 year old to try soy or nut-based milk. Just make sure they are fortified with calcium, vitamin D and B12. That being said, she can meet her nutrition needs without fotified milk, but you have to be on top of it (e.g. adding freshly ground chia or flax seeds into cereal/smoothies and serving kale/brocolli, etc... can boost calcium, adding nutritional yeast on top of pasta/rice/etc...can boost B12, and most kids need a separate vitamin D supplement anyway). I would avoid the soy powder as this is usually intended as an ingredient versus a beverage base and the non-organic powder is sometimes processed with hexane. As for protein, a 1 year old (on average) only needs 10-15 grams/day--eaily met without milk. My daughter really likes homemade ricemilk and you can get creative (e.g. add chia gel for extra calcium) if you want :)
Sara, R.D.