To me it sounds like it could be a lot of fun. Even if the "purpose" is getting her started/getting stuff done. You would be a good influence and able to show the importance of doing your best, and she would know even experienced sewers still make mistakes. Unlike the class you took, it will only be the two of you so there won't be as much of a distraction. It sounds like she's looking for encouragement and companionship, even a mentor.
As to how it would work, why not try once a month and see how it goes. Rather than taking intensive projects have something a little easier (at least in the beginning) that doesn't require as much focus. As to who does what...will it be individual projects or group projects? If it's individual you would each need your own sewing machine.
In my opinion, (I guess that's what all of this is) it would be worth it to try a couple of months and see how it goes. Be positive and upbeat and it should go well for both of you! Good luck!