Re: First boat for small 9 yr old girl?
I think it depends rather where you live and the circumstances in which she will sail.
If you live by a lake or whatever a range of boats will be ok. At least for a time you might want to have either a back up boat available or other older kids with boats.
Otherwise learning in a club fleet, seems to me the way to go, with on water back up coaching boats. That especially in the early stages is not serious racing although some progress to that. With experience she could sail elsewhere.
I would be inclined first to put her through an opti learning program to determine if she actually really likes it. Many clubs supply the boats.