Mother question of ovarian cancer returning

My mother 73 was diagnosed with ovc 4 years ago and underwent massive surgery and chemo.  She now has a small about the size of the tip of your little finger mass which they found on MRI for her hip in the pelvic area.  Her blood work has been normal and her CA125 also has been normal range One time was at 38 but has been running between less then 20 and no higher then 38 that one time usually it is in the low 20 and teens. She also has had both breast removed .  As you can see she is a survivor I guess I just want to know if possible can it return.  She had hysto when she was 38 and breast one removed at 52 and other at 62 ten years later. Three years ago is  when the ovc was found they opened and reconnected her bowl to over ride the area of mass. At that time we were told 6 months but they did not know my mother nor her oncologist.  It had wrapped around intestines. When the surgery was done after several months of chemo they found that one ovary was left and still producing cells.  Just at a loss.  What to do?  She is now waiting to get into gyn/oncologist who did the debulking surgery and her reg. oncologist is great I guess it is for me that I really want to know could the ca return I guess that is a stupid ? yes it can sorry just at a loss.