Hi my indian ringneck is female too, shes roughly 5 years old now maybe abit more.
i know how hard they can bite! Dont dispare it will be ok. She maybe going through the bluffing phase but i cant be sure if so the biting will lessen afrer a few weeks on its own.
its very imortant keep handling her regularly but try not show fear use food to reinforced good behaviour. If i am nervous my ringneck knows and becomes more bossy, or at werst tries to bite me.
She does not use a harness, i cannot train her to use one because i have only the use of one hand so everthing is a little trickier, but we manage
however i do have to use a glove for this reason, she was easy to de sensotyse to the glove and other people handle her without them so she is not totally affriad of hands.
sometimes something really difficult happens because of my disability and i have to start again to biuld extra trust. For instance i accidentally kicked something from an involumtary mustle spasm in my legs, i was barefoot so i got a really bad bruse so i had to get her to fly back to her gage by dropping my arm as it was an imergency but she has forgiven me again now.