Hi Kavitha,
Your surgeon and medical oncologist will decide together which road to go regarding chemo after your mum's surgery (either type), and then you will have much more information. Radiation isn't always suggested, but my Medical Oncologist wanted to blitz the cancer while it was down, after chemo, and I agreed with him. It will be a personal decision between your mum and the Radiation Oncologist. (Yes - GP, Surgeon, Medical Oncologist, Radiation Oncologist!)
The surgeon's nurse will also be able to order a special free bra from Berlei with soft filling to wear after surgery, so your mum will have breasts (for clothes) as soon as she heals. After that, the government repays the cost of prostheses up to $400 each breast, every 2 years, and this is all explained in your My Journey kit, or in fact sheets from your local Cancer Council. Myer does fittings for prostheses and so does DJ's and some bra shops. There is also heaps of information about reconstruction on this site if your mum wants it.
To answer your question about time, my surgery was 16 days after being diagnosed, as Easter fell right in the middle and everyone was away. It didn't make a scrap of difference, so don't worry yourself about it - the cancer has been there for quite a while already and a few days more won't count.
Try just to cope with one day at a time, and don't look too far ahead - it will all happen quite quickly once it starts, so just go with the flow and try not to stress too much. Meditation tapes help and the Cancer Council will probably send you one with all their information sheets. Hope this helps - Michelle xx