installment payments from pooled DC Plan - beneficiary

Pooled investment fund profit sharing plan that used to allow installment payments.  The plan has related rollover funds from an old money purchase plan subject to QJSA rules.    Anyway - participant was receiving monthly payments directly from the plan until 2017 when he passed away.  QJSA and pre-retirement survivor annuity option was waived with proper consent by both participant and spouse.   He was over 70 1/2 and the installment payments more than covered the RMD amount each year.  After he passed away the plan began paying the monthly installment payments to his spouse as beneficiary.  She is also over 70 1/2.  How long can she receive those payments from the plan?  Is there a limited amount of time before the account must be completely distributed out to her as beneficiary?  

This is in the Basic Trust Doc - see item (3):  

(g)   Alternative forms of distribution. Death benefits may be paid to a Participant's Beneficiary in one of the following optional forms of benefits subject to the rules specified in Section 6.8 and the elections made in the Adoption Agreement. Such optional forms of distributions may be elected by the Participant in the event there is an election to waive the Pre‑Retirement Survivor Annuity, and for any death benefits in excess of the Pre‑Retirement Survivor Annuity. However, if no optional form of distribution was elected by the Participant prior to death, then the Participant's Beneficiary may elect the form of distribution.

 

(1)   One lump‑sum payment in cash or in property that is allocated to the Accounts of the Participant at the time of the distribution.

 

(2)   Partial withdrawals.

 

(3)   Payment in monthly, quarterly, semi‑annual, or annual cash installments over a period to be determined by the Participant or the Participant's Beneficiary. In order to provide such installment payments, the Administrator may (A) segregate the aggregate amount thereof in a separate, federally insured savings account, certificate of deposit in a bank or savings and loan association, money market certificate or other liquid short‑term security or (B) purchase a nontransferable annuity Contract for a term certain (with no life contingencies) providing for such payment. After periodic installments commence, the Beneficiary shall have the right to reduce the period over which such periodic installments shall be made, and the cash amount of such periodic installments shall be adjusted accordingly.

Any thoughts appreciated.