How does mastectomy affect women?

Differently. Some seem not to be bothered at all. These generally include the elderly. Younger women tend to undergo a grieving process but this can be significantly diminished by pursuing reconstruction. Reconstruction techniques are so good these days that the reconstructed breast sometimes looks better than the original. Sensory loss and scars arent usually too troubling.
Depends. A mastectomy hopefully will be seen as a benefit to the patient and her family. The issues of loss and fear of the underlying disease are large issues to deal with. With support, time, counseling most mastectomy patients recover well and move forward with all the issues surrounding breast reconstruction.