As your Mother has discomfort, it seems obvious that the LAD needs to be treated. Whether this can be done with stents or whether it requires bypass will be a decision by the Cardiologist. I don't think medication is going to be the answer for long as it is likely such as substantial blockage is going to get worse and probably close the vessel. Exercise would be very difficult anyway, and it won't improve the disease already existing. I think the LAD is the only vessel requiring treatment at this time, and perhaps they can stent rather than bypass.
Invasive bypass, stents are not always sure shot as their might be a case of rejected grafts,clot formation in stents. What's best is EECP. with AMT. Try that and doctors not into EECP would always advise Bypass. If you want highly inexpensive but best EECP treatment then you might try taking free telephonic advice on randhawahospital.com
EECP is an option but in the UK it is only so if there are no other alternatives left. The reason being that most patients require regular top up treatments and the number of collaterals it forces open, if any, is very varied.
Contraindication for EECP: Peripheral artery disease or peripheral vascular disorders (blockages in the arteries or veins of the legs)
I think that venothini should, therfore, follow ed's34 advice - as much as anybody should follow advice given here by non-cardiologists.
The answer to your question really depends on the severity of your symptoms and what the lesions look like on the angiogram. It is best to consult your physician about this question. It would probably be advisable to place a stent in the LAD, however depending on the severity of the other stenosis, your physician may advise open heart surgery. Medical management is another option, however again this depends on the location/severity of the blockages and the severity of symptoms.