Please elaborate. In what year would she have reached age 70½? From your mention of the 5-year rule, it seems that she died before April 1 of the year following the year in which she would have reached age 70½. Unless the 401(k) plan agreement states that the 5-year rule applies unconditionally or unless you explicitly elect by some deadline that payout be based on your life-expectancy, payout based on your life-expectancy is the default, not the 5-year rule.
There is also a special rule that says that RMDs are not required to begin to the surviving spouse under the life-expectancy rule until the year in which the deceased spouse would have reached age 70½.
