I don’t understand why they are not taking taxes out of her $50k art sales income.
After tax art sales income = $50,000 (1-0.25) = $37,500
So required income is $62,500 to maintain standard of living. 62,500/1,120,000 = 5.58%
This means her portfolio needs to return 5.58% real return after tax. Before inflation, it becomes 8.58%. Before tax, it should be 10.09%.