Like the slight majority, I'd mostly leave it alone.
In more detail, I'd compliment her on it from time to time. Once in a while, add in the GE example, and the how to sell at 0% tax angle. I'd seek for 4 of 5 comments to be supportive, with only 1 offering a suggestion or an alternative path. Compliment her thrift, her security, her work ethic, her responsibility.
For your own peace of mind, note to yourself that her SS is bringing her income equal to a $250k investment using the 4% rule. Think of it as the SS being the bonds portion of a portfolio, while the Wal-Mart and the IRA are the stock portion. She's now 50/50 in stock bonds! Perfectly reasonable, perfectly healthy. Heck, if you add up the amount of bonds it takes to produce $1000/mo interest, it's more like 60% bonds and 40% stock already. She has stability plus growth, in case she lives to be 110. Diversification would be nice, but good asset allocation (stock vs fixed income) is even more important, and she's good there. Plus there's zero risk of running short of living expenses; it's only for emergencies anyway, the "fixed income" portion covers her expenses by itself. Plus, in a crash, Wal-Mart has defensive strength - it won't likely go zero. She'll have something available when she needs it.