The statements on the report are quite meaningless, and besides, you can have a blockage of 60% and have no issues, even 70%. What you need to obtain if possible is a nuclear scan of your Mothers heart to see if any areas of the muscle are being affected by lack of blood flow. What looks bad on the Angio report is not always bad in reality and further tests can give much more detail. You don't want her going through bypass or stenting if it isn't necessary. Even if the nuclear scan shows the heart is fine at rest, but reducing in blood flow with exertion, her symptoms will probably be controllable with medication. Personally I think the profession has become a bit too automated. It's like queuing up to see a judge who stamps you as either bypass or stents. Much more information can be gathered first to obtain the absolute best benefits.
For example, ask the Cardiologist "how much is blood flow reduced from the top of the left artery to the bottom" and I bet he won't have an answer. From what I know now, compared to years ago, these are questions I would be asking to ensure they can back up their decisions for best treatment.
The angiogram has determined that she has three vessels blocked. What is important to know is how severe the blockages are. Once they reach 70% they need medical intervention. Whether it's surgery or meds depends on her symptoms, how seveer the blockages and exactly where they are.
Do you have any additional information?