The major difference between Port Orleans
Riverside and Port Orleans
French Quarter, Amy, is theme. Whereas Riverside guests enjoy either a cozy country charm in the bayou section, or a stately southern sophistication in the mansion section, French Quarter guests definitely come "home" to a down-home atmosphere. Think, New Orleans. Both offer subtle southern flair, just in different ways. You can get an idea of those differences by checking out pictures of both via the links I provided in the first sentence of my answer. In addition to the varying themes, French Quarter is a bit smaller than Riverside. Also, Riverside offers a sit-down restaurant whereas French Quarter does not.
I can't really choose one over the other based on the preferences of your daughter, only because I truly think she'd be happy with either. French Quarter offers a pool that is more eye-catching for the younger set, though Riverside's pool has provided hours of entertainment for my kiddos. On one hand, Riverside's resident piano man puts on a GREAT family-friendly show in the lounge. On the other hand, French Quarter offers a colorful food court with delicious beignets. See what I mean? It all equals out in the end. I would base my decision off of your personal preferences and rest assured that she'll have a magical vacation no matter which you choose. Enjoy!