Pub 559 from the IRS indicates that she can roll it over tax free to a number of different destinations:
"Rollover distributions. An employee's surviving spouse who receives an eligible rollover distribution may roll it over tax free into an IRA, a qualified plan, a section 403 annuity, or a section 457 plan. For more information, see Pub. 575, Pension and Annuity Income, and Form 4972, Tax on Lump-Sum Distributions."
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https://www.irs.gov/publications/p559Since the amount is sizeable, as
@Mouse21 said, she probably can leave it in her husband's plan as well. (If it were a small amount, the employer might have rules that they could force a disbursement, which would probably best be handled as a rollover distribution above.)
I think if she rolled it into an IRA, it might be treated as an inherited IRA at that point. If so, she would *not* be eligible to perform Roth conversions from an inherited IRA.
I'm not 100% sure I agree that she would not be required to drain the account within 10 years. That may have been true for @Mouse51, but I think in general it depends on a number of factors. Pub 590-B would contain information about IRA distributions requirements and whether she would be subject to a 5-year, 10-year, or lifetime-RMD-type requirement.
As far as investment AA goes, it should be invested according to the widow's goals, facts, and circumstances, which may very well now be different than her husband's goals, facts, and circumstances when he was alive.
Sorry the life insurance people are being a pain. There should be some state or federal agency which supervises them, and a phone call of complaint may get things rolling along there. As a point of reference, my Mom's life insurance proceeds were deposited into my account about 49 days after she died, but we were pretty organized.