Actually not. $2.8 million of that total is tax-exempt. She therefore paid taxes on a "mere" $2.3 million of taxable income. So presumably she had a relatively low cash on cash return on her investments or she is sheltering a hell of a lot.
As I pointed out 10 year Treasury bonds pay 4.25% (today at historically low rates). If she had $425,000,000 in Treasuries her income from that would have been over $18,000,000, where the heck does one "shelter" nearly $16,000,000 in taxable income?
I guess that's their "fair share."