My condolences.
I agree that the first place to start is to contact the plan administrator. The provisions of the QDRO and the plan would govern, and I have seen great variations between QDROs.
While, as ESOP Guy indicates, as a general rule spouses have rights under defined benefit plans, the same is not generally true for spouses of spouses. It is my understanding that, in general, no protections are required by law for the spouse of an alternate payee under a defined benefit plan, and the marriage of the alternate payee would not automatically override prior beneficiary designations (the way it would if a participant were to designate a beneficiary and then marry).
I have seen separate property QDROs that restored the alternate payee's benefit to the participant in the event the alternate payee died before commencement of benefits. The provisions of the QDRO (if any - many QDROs do not say what to do in many possible contingencies) concerning what to do in the event of the death of the Alternate Payee would govern. So you will need to go to the plan administrator to find out what rights, if any, you may have.