Late to this so sorry if you already made a decision.
I'm not sure the handedness of the instrument is the issue, after all you don't have a left handed saxophone AFAIK. Young minds are more adaptable and I reckon she'd be fine on either. Of greater importance is general comfort. 9yo might be too young for a full size guitar - I suspect it is. Therefore getting something that fits her body and arms is important. I'd also think carefully about nylon vs wound strings. The biggest issue for most learners is the pain of fingering the strings (fretting hand). A classical guitar with nylon strings will alleviate this but sometimes the neck width can be too wide for kids to get their fingers around especially for barre chords. If it was me I'd be looking for a nylon stringed 3/4 size with as narrow a nut as possible.