Thanks for the responses. I unlinked the box from my account last December, and gave it to her at that time. It has been rebooted many times since then (especially around the time of the Netflix upgrade, when we were rebooting daily trying to get it to work, LOL!). Going into the Channel Store gave no option to link it to a roku account.
We have not reset it to factory specs as I recall. We will try that tomorrow. Thanks for the help, guys! If worse comes to worse I will call Roku now that the weekend is over, and I will post the results here.