It's great that you want to help your sister. I live on my own now, but when my husband was alive the hardest thing about sharing a home was trying to hold on for the bathroom if he was in there. He loved long, leisurely baths and unfortunately we didn't have a separate toilet. I used to feel bad about hauling him out when I was desperate but he was very good about it. I think being considerate about food is also good, not trying to get a person with Crohns to eat anything they're uncomfortable with, and maybe changing your eating patterns a bit to fit in slightly - for example, if your sister can eat baked potatoes, have baked potatoes for tea several times a week.