Basic mending: repair a hem, replace a button, shorten a garment.
Basic tools and how to use them: scissors, needles, pins, measuring tape, thimble.
Sew curtains, pillows, aprons, or other home decor. I don't think I would tackle clothing unless she showed some interest in it; nowadays store-bought clothing is usually cheaper than homemade.
The cookies project sounds like a winner! Maybe also some basic easy meals: spaghetti, tacos, baked chicken, etc. Of course salad, baked potatoes. Some grocery shopping lessons!