Hi, you ask some very good questions and I think you are very wise to ask them. It's good to see you care so much about your Mother :)
I was quoted the 1 in 5 chance of not surviving, but you have to take certain things into account. Before surgery, usually one or two days before, they should give your Mother a Lung function test. This is an important factor in survival. You need a good strong set of lungs to overcome ANY major surgery. If they don't have such a test scheduled, then I would ask them to organise one. I also had a doppler test of my Carotid arteries in the neck to make sure there were no problems there which are likely to cause stroke or heart attack. This is also non invasive, it's simply a type of echo scan. Blood tests before surgery are also important to ensure there are no infections lurking around. If certain cell types are high, it can be an indication of infection and it would be wise to delay surgery. Even a tiny infection in the Lung for example can lead to serious pneumonia and life support after. You say your Mother is active, this is a good thing and I assume she isn't drastically over weight. It is also a good measure to ensure they take swabs of her groin, arm pits, mouth and have them tested before surgery to ensure she hasn't picked up any infections from the hospital or other patients. This is commonly done in the UK to check for such things as MRSA. Showering twice a day for a few days before surgery is also important to keep the skin as clean as possible. When your Mother leaves the shower in the evening, she should be put into a bed with clean sheets. No physical contact with any other patients over those few days. This is how strict they are in Heart hospitals in the UK. Even visitors were not allowed to touch me, which was hard because there's always that reassuring cuddle. In the operating theatre you have to remember they have a lot of equipment there if any problems occur. They have bypass machines, defribillators, pacemakers, ecg monitors, blood pressure monitors and a whole host of other equipment.
Talk to the surgeon about the procedure and ask him to use BOTH the arteries from her chest if they are in good condition, both the LIMA and RIMA. These last much longer than veins and give much less problems. I only had the LIMA used with 2 veins and after 3 months the veins failed. The LIMA is still working great, 3 years later.
Being an honest person, I will not lie to you. There is some discomfort but your Mother MUST tell them if the pain relief medication is insufficient, there is always room to boost it.
She will not feel like eating for a couple of days, but then the recovery starts to happen quickly. In a few weeks she will be walking around much improved and feeling much better in herself. Discomfort time varies among people, but from what Ive witnessed, I would say it lasts anywhere between 6 and 12 months. This is NOT terrible pain, its like a muscle ache.
After about three weeks you find that you can stop the heavy pain killers and just take mild ones. She will need to rest a lot, but after 3 days from surgery I was walking around the ward. If she is determined, she will also be on her feet quickly. It's best to just keep thinking "the worst is over, now all I have to do is recover, no more surgery now".
For the first 2 days there will be 2 or 3 plastic tubes coming out from the bottom of the chest into containers. When no more blood leaks into these, they can be removed. This is not at all painful, it's a relief.
The last thing I would like to mention which scares a lot of people, is waking up with a breathing tube down your throat. I am very scared when it comes to such things, but I was sedated quite heavily. I was shocked to find that I couldn't feel the tube and it felt nice that it was breathing for me, it was like having a holiday from my body. The only part which makes you panic and gag, is when they insert a tube, but this is done when you are asleep so you know nothing about it. When they take it out, there is no discomfort whatsoever. Your throat just feels a bit dry after. So don't believe any scary stories about these things.
If you need to know anything else, or your Mother has any questions, PLEASE don't hesitate to ask. I know it's frightening when you know you are going to have bypass surgery. I was scared out of my wits but when it was all over, I kept asking myself why I was so afraid.