Wow, she is lucky to have you!  It's wonderful how you've fully thought
of it from her angle to help her (I liked the thought that she's trying
to teach you to play fair!).  I wasn't going to write with advice, just
to support what you're doing.  But after you mentioned what you already
tried, I figure I would mention what worked for me when Mikette was a
biter.  It may not be a good idea to try with Oracle (you will know
whether to or not) if her biting is fear based.  Mikette used to go
around chomping ankles and wrists of visiting guests.  What I did is get
a spray bottle of water and give her a small mist and say "NO BITE" when
she bit someone.  Then when she started to associate the water with the
biting I would get out the bottle and give a warning spray next to her
and remind her "no bite" when she was sniffing suspiciously around a
friend's ankle.  After while when guests came I could just put the bottle
in her sight and remind her "no bite".  Eventually we didn't need it at
all.
 
Mikette passed two weeks ago, but hadn't been a biter in years.  At some
point in her illness and being cared for she became a kisser.  Fingers,
cheeks, lips, even noses (her old favorite nip spot!) would receive
non-stop kisses.  She'll always be known for her nips, but remembered by
her kisses!
 
Much luck with Oracle, and all others awaiting a ferret whisperer
 
Risa
[Posted in FML issue 5223]