It doesn't matter how they spell it; she'll still be
Abby. Nothin' wrong with
Abby, but if you're going to love a popular name,
embrace it. Don't pull a kre8tyve spelling out of your ass and act like you're original for using it.
Of course, there is always the chance they just liked this spelling more than the original...and as a
Rachael, I should be more sensitive to that sort of thing. Heh.