If your policy is no refunds, send her a copy of the contract.
As a courtesy you can also send her an itemized receipt.
I would also Explain the deposit she paid covers not only cancellation, but the care she received, and that she was on your schedule. Most clients have no idea what it means to be on a birth workers on call schedule. They don't realize that we don't take other clients (that is our livelihood) when we receive a deposit.