In Kingdom Hearts (the popular Disney/Final Fantasy game) Alice is one of the 7 "Princess" of Heart
Princesses of Heart are not based of their royal statsis they are based on their heart which are pure of light.
I guess what I'm trying to say is that "Princess" is not just TITLE oriented, it's the heart that counts.
That and Alice has done so much for Disney (for a heroine that's not a part of the Disney Princess franchise) and is such a big influence to kids:
1. Alice was created when Walt Disney was still alive, and I believe any Disney animation women of his work should be included in the line up.
2. Alice was involved a lot in Disney both before and after Walt Disney's Death with the current Disney characters in both time eras.
3. Alice didn't need a love interest to save her. Even though she got herself in situations, she was smart enough to get out of them.
4. Alice might be 12 years old, but she was brave and strong minded to stand up for herself this will influence girls to stand up for themselves (not wait for Prince Charming all the time).
5. With Alice in the Disney princess line up she will symbolise youth. And younger Disney fans (4-7 years old) are more likely to approach her without ease than the older princesses, because kids like to approach Disney characters who look youthful and kid friendly.
6. Alice inspires kids to use more of their imagination. Because Wonderland is based on Alice's imagination and on what Alice thinks of her own ideal world.
7. Out of the other Disney animated women who are not part of the Disney princess line up. Alice was included, but unfortunately got kicked out. But even though she got kicked out, Alice out of of the Disney non-princesses animated women was included more frequently in the Disney princess franchise.
To be blunt: Wonderland is just a great place to put into a computer game. Because of this, Alice was included in Kingdom Hearts. And that's it. Though I personally think that it just makes her a "princess of the kingdom hearts game" and not a "disney princess", despite what Wikipedia says.