I would send her another note asking her to kindly let you know when the package has arrived at which time you can discuss whether she wants to keep it or return it. This will, hopefully, avoid a situation where she simply writes "return" on it, or declines it altogether, in which case when (and if) it finally reaches you, you will have to pay the return postage.
You say she is new to eBay, so she will likely think this is a reasonable request and work with you. A seasoned buyer with a fraudulent bent may readily understand from your request that you have not shipped with tracking and might start playing games.
In the end, you will have to decide, based on the value of the item, whether it is worth the cost of return shipping. Or, you may offer her a discount on the item and provide a partial refund.
Good luck!