Since she's getting back into it, I'd assume she already does, but if she doesn't have a good quality iron and fabric scissors already, I'd definitely start there. I spend more time with my iron than my sewing machine and there is nothing so frustrating as bad scissors.
In the making life 100x easier categories I would include a dress form, silicone fingertips for ironing, and a bias tape maker. I haven't actually used the last, but hot damn do I want one! Definitely suss out if she likes using bias tape or not though.
Other useful stuff: rotary cutter, mat, and clear ruler, Specialty scissors (pinking shears, applique, etc.), Sewing machine feet (walking, quarter inch, binding, ruffler, etc.), Rulers (variform, hip curve, etc) for making or adjusting patterns