I once had a thread where I suggested that the main characters could be paired with GFs they resembled physically or in terms of personality. My thought was Carbuncle for Selphie: both are bouncy, cheery and cutesy.

In terms of her original GF, parsimony would suggest one of the extant ones that the party eventually gets, although there's no reason there can't be other GFs the party never finds. She even could have junctioned to Tiamat in his GF days.

Not that I'm suggesting either is likely.