@ladyjane - Many women your mother's age experience bladder prolapse symptoms whether they've had surgery or not. Unfortunately it's caused from aging, childbirth and even menopause which weakens the vaginal muscles.
It is very likely that your mother will have to undergo colpocleisis surgery again to lift the anterior vaginal wall some more.
This type of surgery almost always involves the risk of recurrence due to the fact that the muscles and nerves continue to weaken as we age.
Unfortunately the second surgery might not have as good of results as the first one because the tissues are worn thin and oftentimes a special graft must be used to support the vaginal wall.
If she has gone through menopause and there's no chance she will ever have children again then another option for her to consider is a hysterectomy to remove the uterus.
The best advise of course will come from her physician. Together they should discuss her options to better know what is the right choice for her. I hope this helps answer your questions. Good luck to the both of you.