She doesn't have $30,000 of income, she has $110,000 of income (including the taxable $80,000 of capital gains).
Depending on how much Social Security she has (only part of it would be taxable) , if she files as Single and takes the Standard Deduction, that leaves roughly $95,000 of "taxable income". That puts about $55,000 of that capital gain income in the 15% tax bracket.
So between the 'regular' tax on her other income and the 15% tax on the roughly $55,000 of capital gain, yes, about $9000 in Federal tax is probably correct.
