I know that this may seem weird, but we have seen nothing that indicates that Alice paints her nails.
We have seen a scene of the boy's sister do it, but never Alice. Additionally she sleeps without bothering to clear it, there doesn't seem to be chipofs (though that could just be the author not bothering to do such a tiny nonsensical touch)
Either way, seeing her as child having her nails painted made me think. What if they aren't painted but are naturally like that? And that has something to do with their species.
For example, I can't see stupid Caph putting on nail polish every other day. She seems like the type that would growl and just stop with such a bothersome task. Which likely means her nails are naturally like this.
I am totally overthinking this, but I still think what I saidmight hold some nugget of truth.