I don't know your mom, but I do know that there's very little you can hand off to someone else as a failure-proof turnkey system that will make them decent money indefinitely while also being enjoyable most of the time (unless you're just going to straight up hire her for specific tasks on an ongoing basis). Failure and experimentation are so crucial to most of what we do, and someone who can't deal with that without getting discouraged and quitting is going to have a hard time eve getting anywhere.
Perhaps the most important thing, if your mom is anything like mine - are you prepared to spend hours and hours answering questions and explaining things, then answering more questions when something changes, when her site gets hacked, when she needs some little thing modified, etc? If she has the kind of personality where you know she'll be very independent about it and pursue her own solutions to problems, it might not be so bad, but a lot of adults have a weird learned helplessness or insecurity about the internet. That can cause you a lot of headaches if you're not careful.