I would say that she needs to wait at least three weeks. She really needs to wait for some times in order for the surgery to heal completely before she puts any makeup near her eyes. I hope that this helped you and your grandmother a bit.
Of course. But you must wait for some time until the surgery get healed completely. It usually takes two or three weeks that you can wear mascara after cataract surgery. If you wear mascara soon after cataract surgery, it can cause inflammation which can delay the healing process. So you'd better wear mascara three weeks after cataract surgery.