did they not mention anything about collaterals being present? These are natural bypass vessels which open. What about you? if your Mother has this disease then you should have your blood pressure checked.
According to the report, there are blockages in all three coronary arteries.
The LAD, with 70% stenosis is probably not in immediate need for intervention.
The two most dominant vessels (LCX and RCA) with 80% stenosis in the LCX and 3 critical lesions in the RCA need to be treated soon.
When blockages are found in more than 1 vessel and in multiple locations per vessel, by-pass surgery is normally advised.
As an alternative to by-pass surgery, I can image that it could be treated with stents too. It would however take at least 4 and probably more (6?) stents to solve the problem.
You could discuss with your cardiologist if this could be a solution for your mother and if he is willing to try it.
Critical blockages can not be treated with medications only.
Good luck and please let me know what is decided.