Moneygram, Western Union or Walmart money transfer. There will be a significant fee.
Don't send cash through the main, but you could send a check ov money order.
Go to the post office and ask for a money order. You give them the amount of money, and they give you a piece of paper with the amount, which you send to your sister.
you can still send her a check and she can take it to any branch of union bank in IL to cash it
Money order
paypal