I'd like to think human biology isn't even capable of blanking out like that. Every hundred years or so of not aging, you effectively reset as a person, as every cell in your body has reformed and all your older memories have long faded. There's also the possibility that Alice was just "built different". As a claimed "Goddess", immortality comes naturally. Does it not?I don't get why you've made Alice as old as you have. When you start moving into the millions of years old range human concepts of time struggle to get you anywhere fathomable. Human history can barely hit 6 thousand years, we've only been building permanent settlements for about 12 thousand... as a species we've only existed for about 200 thousand, a fifth of a million years, and here you have a bunny girl who has lived the entire existence of all of humanity over and over and over so many god damn times over... how could such a being have anything left to offer its own mind? Immortality would be a complete prison, stuck watching the same tv show, heck, the same episode, on repeat for decades with nothing else to do in that box. You'd watch tree after tree grow in the exact same spot, the billions of faces to come and go, they'd all look the same eventually... there's just no way a person can sit down and try imagining this for any real length of time and come up with something that isn't completely horrifying. Even a million years would be an unbearably long life and you've got this girl still able to hold a conversation after i think it was 100 million? Alice should be a comatose vegetable statue sitting frozen in a shrine, long forgotten at best, as some creepy living statue curiosity in some museum at worst.
This is, I guess, the "optimistic" interpretation of how a person would be after living for millions of years, as opposed to the recently popular pessimistic ideas. A lot of the more bleak problems of immortality are fortunately solved in a magical world with healing magic.
The unspecific million or millions of years are pretty important to the story, so it was more of a necessity than anything. Ultimately, it's not a super important detail to the grand narrative. Perhaps I should have been even more vague about her age rather than pinning a number onto it, but I don't think anyone, including myself, should worry about it too much.