Don't assume that she can do it. However, for someone who cannot physically do something, there is always a way if they truly want to do something.
Yes, we usually use our right hand to hold fabrics together. Who says we have to do it with our right? Our left can reach over and do it for us, if we really want to do something!
So take a patience pill and help her start with something simple to help her get used to working with the sewing machine and fabric ... and to figure out some of the innovative ways to make it happen.
She CAN do it ... and we'll all look forward to seeing the results!
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You asked if there was any quilt she can do without pieceing. Whole cloth quilts are always an option ... either using yardage or cheater quilt fabric or a pre-printed panel.