Others with this ailment/difficulty can give hints as to what worked for them, but I agree that talking with an occupational therapist would be helpful and likely not harmful. Occupational therapists are usually with the "rehab" group, so that is a good place to look.
Changes in her set up may need to be made such as: more ergonomic placing of her sewing machine--higher and tilted, tables for cutting may need to be elevated, etc. This is what the occupational therapist can assist your friend in doing.
My thoughts/prayers are with your friend for a full speedy recovery. Good Luck!