Jeane was examined thoroughly by Lilly in the bath scene in Suikoden 3, the chronologically latest Suikoden. Apparently this was because Lilly met her as a child in Tinto in Suikoden 2. And Jeane hadn't changed at all.
There's a lot of theories flying around about who/what Jeane is. But apparently only Koroku knows her secret.
But in Suiko5 we at least learn that she's famous in the mages' circuit (Zerase, Eresh, Leknaat seem to know something of who she is).
And that clue about there being TWO unique things about her made me think of Viki more than Jeane (specifically because of the two Vikis in S3).
-Djinn