Carole's response was very drastic and ignors the seriousness of that type of surgery.
You do not need to use a bag with an indwelling catheter. You can now get excellent valves which just plug into the catheter. I use one all the time and it's meant I can return to swimming, enjoy a bath etc.
You just switch it over every 5 days, simple!!!
Think at 83 to expect surgery is not in the best interests of your mother-in-law.