Okay, I didn't see a thread for her already, so I decided to start a one.
Does anyone know what her maiden name is?
That's all I want to know...
No, officially, we do not. However, Neville was a pureblood, and there really aren't that many purebloods to choose from, so you'd probably want to keep it with one of the pureblood families we'd heard of, unless you want to make it a family for whom she was an only child, and the last one to bear the name.
While any pure-blood family will fit with canon, I always liked the idea of Alice's maiden name being Prince, making Neville a relation of Severus's. I liked the idea that it would add to why Snape was so cruel to Neville; both their mothers were pure-blood Princes but Neville was accorded the status that Snape always wanted.
I'm not sure if that will help you with your story in any way, but I'd advise choosing a family name for Alice while keeping in mind who will become related to who else as a result.
I like Hypatia's theory it sounds like fun and it would give your story a great sub-plot to work with.
I was wondering...
Since Neville was a... candidate (for lack of a better word) for the prophecy, how did his parents thrice defy Voldemort? Is there any canon evidence?
I don't think there is any canon evidence, but Neville's a pureblood who has absolutely no blood prejudice, so I think one of those things would involve shunning the Dark Lord's politics.
Alice and Frank were also both Aurors, and as such reasonably likely to have been involved with catching and/or persecuting his Death Eaters, which is not likely to endear them to him.
Perhaps the third was joining the Order?
I'm sure that I read an interview with Rowling where she stated that Alice's maiden name is Johnson or Prewett, but she didn't have her notes so she couldn't specify which. I've read a few fanfics where Alice's last name was Hinton.
Hufflepuff seems a natural house for Alice in my mind, but I've got nothing to support it.