WA state estate planning laws, do beneficiaries identified in IRA need to be identified in a Will

You'll love this answer: It depends. There are tax advantages to naming a beneficiary on an IRA -- the distribution schedule is based on the life expectancy of the beneficiary. And the IRA with a beneficiary designation does bypass the will (and probate). However, often a Will contains restrictions such as a trust for a beneficiary that would be skipped if the IRA did not list the trust (or estate) as a beneficiary. There are ways around this but I would suggest that you consider reviewing the Will with an attorney to make sure your mother's intentions are fulfilled.

Need to? No. Actually I would caution anyone against subjecting an IRA to probate. The value of the IRA will be part of the estate for estate tax purposes regardless of whether the IRA is paid directly to a beneficiary or made part of the estate for probate purposes. There is nothing your mother can do in her will regarding the distribution of the IRA that can't be done directly with the IRA beneficiary form (including, perhaps, a trust if desired) thus bypassing probate.

One primary reason for including the IRA in her will would be to create as a testamentary instrument some distribution device that woudl be more expensive to create outside the will; for example a trust that needs to be funded before her death to continue existing after her death to receive the IRA proceeds. Other than that just ignore the IRA in her will.