I'm just wondering if it seems southern/countryish, because you live in the South? Because I think pretty much any name said in a thick Southern accent sounds southern. If not, maybe it's just because there are a lot of southern names that use Leigh
in the female form, sometimes just as a pet name.
I think Rosalie
will sound different in different accents, in different places. If you say it the way you want it to be said, and keep reiterating that point then those that are close to her will say it the way you do.
However if you really don't love the name, good luck in your quest. :)