My wife is selling her property abroad. She will be paying capital gains tax of 6%, documentary stamps at 1.5%, and commissions to the broker. Does she still have to pay taxes here in case she brings the money back to the U.S.

If your wife is a U.S. citizen or resident, she must report the sale of the U.S. tax return. She must report the sale. She will also claim credit for taxes paid in the foreign country by filing Form 1116.
Read: Your U.S. Tax Return: U.S. Citizen or Resident with Foreign Income