I am so sorry to hear about your mother's diagnosis and I can imagine how scared and confused you must feel. The radiotherapy was administered on my husband for five weeks every weekday, so he had weekends off. I think this is the normal protocol but it would be a good idea to ask your mother's oncologist any questions you want answered. Every case is different and everyone responds in their own way to treatment, so while she may have bladder and bowel problems, she may not. Certainly towards the end of treatment she may feel more tired and may have diarrhoea. You note I say "may"! As I say, everyone responds differently.
Is she also to get chemotherapy? Do you know what stage she has? These are the useful questions to ask her medical team. To encourage you, my husband, nearly 65 at the time, was dx Stage 111C nearly four years ago. He had eight months of chemotherapy and 5 weeks of radiotherapy as well as prostate problems running concurrently, so he did not have an easy time. However, he is doing so well right now...working full time and very nearly back to normal. He does have urgency to use the bathroom but has it under control.
I wish you and your mother the very best. Post back with any questions that we might be able to help with.