You can place it in listening mode by holding the setup button. You can then use the Particle app to configure the credentials without claiming the device. No special SoftAP code needed.
You can have the SoftAP code work when there's no connection though, which is a valid alternative.
She'd need to have physical access, yes, but not claim it. Both the CLI and the app can be used to configure credentials without actually claiming the device to an account.
What I was getting at was that if you knew her wifi credentials, you could pre-configure it using either the CLI (over serial), or in code. That way, no further interaction would be required when she gets home.
If you want to make it even more complex, you could make the lamp a 'product' in the console, where you're the product creator, and she's the customer. That way, she can claim it to an account, but you keep the possibility to flash new code. I wouldn't take it that far though.
The easiest solution would be for her to hold the mode button and use the app.