Any blocked artery leading to the heart is dangerous. But your mother should recover and lead a normal life. She will have a drastic change in her diet. She must follow that change for the rest of her life. Period. She will have drainage tubes in her chest after the surgery and she will have the long scar down the center of her chest, which will be somewhat swollen for a time, there will be soreness there and she should hug a pillow whenever rising off a flat surface, like a sofa or bed, or when standing after sitting for a period of time. This is to reduce strain and pain on the incision. Patients heal rapidly and the scar will fade to a simple fine line in time. After her surgery, she may actually end up back in surgery again, to suction out drainage fluids, this sometimes happens and is not unusual. Do not panic if they have to open her back up to check drainage tubes. She will have tubes in for a short time, then they will be removed. When she is able, go with mom for short walks in the hospital halls, she will probably have to hug a pillow on these walks, and take your arm, go slowly, she will regain her strength, but not in the hospital, it will take time. They will remove a section of vein from one of her legs and will use that to bypass the clogged section of artery, creating a new passageway for blood to the heart. Most patients complain that the scar and incision in the leg is far more painful than the one in their chest! Follow her doctor's instructions to the letter. Good luck to you both.
Close family member had a quintuple bypass.