I am sorry that your Mom is having problems. Does your Mom already have an Ostomy?Ileostomy or Colostomy? There is a lot more of the small bowel than there is of the large bowel(Colon) And I know that you can live without the large bowel because I dont have mine anymore. If its her small bowel that is having the perforations, then I think what happens is, the surgeons remove the section of bowel that is causing the trouble and rejoins the small bowel back together. I don't know how much can be safely removed before absorbsion etc would become a problem though.
Did your Mom start of with liquids and then soups before she started back on a proper diet? Maybe she went onto solid foods a bit too quickly.
I hope that she gets the help that she needs at the next hospital.