If you want ridiculously simple, you could put everything into either Vanguard's Wellesley Income (
VWINX) or Wellington (
VWELX).
Wellesley is a balanced fund mix, and the most conservative of the two with 1/3 in stocks and 2/3 in bonds. It will throw off some decent dividends each month (the income part) that could be reinvested if not needed.
Wellington is also a balanced fund mix, but skewed the other direction; 1/3 bonds and 2/3 stocks. So still conservative, but better growth opportunities.
Do also consider if any of the invested funds are in a taxable account, or IRA required minimum distributions (which she will have to take each year) may push her up into a higher income bracket. As she is single, her social security and distributions all will have impact her taxes. So investing heavily in bonds will add to her income through the dividends/cap gains generated.
If you can't decide, an equal mix of Wellington and Wellesley will give you 50% equities and 50% investment grade intermediate bonds. I personally would choose one or the other and go 100% into that since it's so easy and it's Vanguard so you know they are excellent funds - just have to decide
very conservative (Wellesley) or reasonably conservative (Wellington) basically.
Both are considered the gold standard (and highly recommended) for conservative portfolios (so will weather downturns as well as anything) while still providing a bit of growth.
You could recreate the above if for some reason you'd prefer using Vanguard's VTSAX and VBTLX (both of these are their all encompassing index funds) to create a 60/40 or 70/30 2-fund portfolio.
Vanguard Total Stock Market Index Fund (VTSAX)
Vanguard Total Bond Market Index Fund (VBTLX)