My personal pet theory and explanation for her inexplicably different appearances is that Alice's actually an incorporeal spirit who inhabits appropriately enchanted puppets as her physical vessels, and simply pragmatically opted for an "adult" form when she decided to move out of Makai. (This idea might or might not have been lowkey inspired by Aozaki Touko from Kara no Kyoukai and some sci-fi themes >_>) Sorta takes her puppeteer motif to its logical conclusion and, well, it's not like the canon says anything about what she looks like under her dress... o3o
^Sorry, this artist nuked all of their websites and accounts a few months ago, including the Twitter account this was originally posted on. There's nothing left (except for everything that was reposted on Danbooru)