One of our valued employees retired a couple years ago at age 66 and took a lump sum distribution from our DB plan. We occasionally had her back for a day or two but now am contemplating having her back more or less full time for about 2 months. The plan says we have to suspend her pension during that period.

What pension? Does she have one? If she has one, what do we do? Anybody faced this before?

If she's been cashed out for all of her accrued benefits through a lump sum payment, she doesn't have a 'pension' remaining.

As a practical matter, the suspension doesn't apply to a returning retiree who previously took such a lump sum and is not receiving nor entitled to any further payments. There are no benefit payments to suspend. Rather, the suspension issue applies to those that receive periodic annuity payments rather than having elected the lump sum option your plan apparently permits.