Don't you just "love" government "reasoning"?

Only the government would think it reasonable to continue paying health premiums for a dead ex-spouse.

Death of Ex-Spouse Does Not Qualify as Status Change for Cafeteria Plan 

The IRS stated that the death of an ex-spouse does qualify as a “change in status” for altering benefit elections made under an IRC §125 cafeteria plan [IRS Information Letter 2019-0013, 6-28-19].

An employer asked if an employee could change his cafeteria plan deductions after his former spouse died during the middle of the plan year. The employee was providing health benefits in his cafeteria plan to his former spouse because of a court order and wanted to change his election after her death.

Generally, employees must make irrevocable benefit elections under a cafeteria plan before the benefit becomes available or the plan year begins, whichever is first. Changes or revocations during the plan year are allowed only under limited events:
     (1) Marital status changes.
     (2) Change in number of dependents.
     (3) Employment status change 
     (4) Change in dependent or adult child status.
     (5) Residence change.
     (6) Adoptions.

Under IRC §152(a), in general, a “dependent” means a qualifying child or qualifying relative. A former spouse is not a dependent under IRC §152, so the death of a former spouse does not change the number of dependents and is not a change in status under the regulations. The regulations also do not provide that the death of an employee’s former spouse that nullifies a court order providing for the former spouse’s health coverage results in a change in status. Although Treas. Reg. §1.125-4(d)(1) provides that cafeteria plans may treat certain court orders requiring health coverage for an employee’s child as a change in status, the regulations do not include the death of a former spouse. The employee will be permitted to change his cafeteria plan elections, including dropping coverage, as part of the next annual open enrollment period.