Can IBS stop you from working?

My 23 year old sister has had stomach and bowel problems in the last 2 years and has even been hospitalized 3 times with the pains. They thought it was appendicitis at first and then told her she was just constipated. She has had a sigmoidoscopy due to bleeding from the back page and ultrasound scans and lots of blood-work done. The last blood results showed up inflammation and is awaiting results to find out whats causing it. She gets extremely bad cramps and her doctor has put her on the sick for IBS. She has to attend a medical about it and is worried they wont p her. Can IBS actually get so bad it stops you from working?? Thanks.