This is a gorgeous, uncommon variant of Alexandra. Sure, the Alex- family of names is *huge*, and the ability to fall back on the familiar "Alex" is still present. But I'm surprised Alexandrie doesn't get more use even in France. It's beautiful.
First time hearing of Alexandrie. I like it! It's very different but at the same time has a familiar sound thanks to it's other more popular "Alex-" counterparts.