​Mining magnate Gina Rinehart's oldest and youngest daughters are so distrustful of one another that Bianca has required her sister Ginia to sign a confidentiality agreement before making her privy to legal action concerning the trust to which she is a beneficiary.

Bianca Rinehart, who is trustee of the multibillion dollar Hope Margaret Hancock Trust, is seeking judicial advice from the NSW Supreme Court that will include a discussion of legal tactics, following the court's approval for her to sue Gina Rinehart over her management of the trust between 1992 and 2015.

Ginia Rinehart supported her mining mogul mother Gina Rinehart in a case brought by her siblings in 2015. Credit:Philip Gostelow

Bianca's barrister Christopher Withers applied on Thursday for extensive secrecy provisions that included requiring Ginia Rinehart and her legal advisors to sign confidentiality agreements and closing the court for the proceedings.

"The issue is not so much with Ginia, it's in terms of the problem with Mrs Rinehart who is the mother and the former trustee," Mr Withers explained.