You should post this question in the divorce/family law forum. Divorce laws differ in every state but, in general, unless she can prove some form of "duress" the separation agreement is a legal binding contract.
You'll need to have your attorney review the agreement. As mentioned by Mr, Cassara, state laws vary, and also nobody can interpret the separation agreement without reading it.
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I can only make some general comments which aren't legal advice, since I don't practice law in Washington or hold licensure there, but if memory serves, Washington is a community property state. Just applying general principles of law, to the extent someone was accruing retirement benefits during a marriage in a community property state, it seems likely to me that the person's spouse has a claim on some portion of the retirement as an asset of the community. But the extent of that claim is something which needs to be evaluated by a lawyer who handles divorces in Washington and is knowledgeable about dividing military pensions, qualified domestic relations orders, and related matters. You should consult such a lawyer.
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