(1) A beneficiary may disclaim an interest in whole or in part, or with reference to specific parts, shares or assets, in the manner provided in RCW 11.86.031.
(2) Likewise, a beneficiary may so disclaim through an agent or attorney so authorized by written instrument.
(3) A personal representative, guardian, attorney-in-fact if authorized under a durable power of attorney under chapter 11.125 RCW, or other legal representative of the estate of a minor, incompetent, or deceased beneficiary, may so disclaim on behalf of the beneficiary, with or without court order, if:
(a) The legal representative deems the disclaimer to be in the best interests of those interested in the estate of the beneficiary and of those who take the disclaimed interest because of the disclaimer, and not detrimental to the best interests of the beneficiary; and
(b) In the case of a conservatorship, no order has been issued under RCW 11.130.435 determining that the disclaimer is not in the best interests of the beneficiary.