I agree that you should try to get her set up at her house, as she needs to be able to work on her projects at her home. Not sure what her mobility limitations might be, but if she is readily mobile and looking meet people through quilting, you could help her find a bee or a guild...that way she has the option to quilt at home or with a group. She will likely pick up quilting tips from others as well. I would not want to risk the possibility that she might fall while navigating your stairs, nor the liability issues that might come from it. Better for you to teach her at her house also because you can politely end the lesson when you feel and can leave more in a timely manner from her house than she could from yours.