Ulcerated Colitis and bowel cleansing

Hello my question is for my sister who has ulcerated colitis, I want to try and help her, I've got gall bladder probs which I'm happy to say are increasingly getting better with the flushes I'm doing, doing my 8th this Friday my gall bladder is telling my it's time. I know with alot of Bowel Cleanses if you have this condition (colitis) they can be too hard on the bowel especially if they contain cascara sagrada and the like. I looked into Dr Gray's formula and he says on his web site not to do this if you have this condition and his formula doesn't contain cascara sagrada so I'm not sure why he says not to do his, how are you suppose to help this condition without cleansing first?

Would P&B shakes be the gentlest? I love The Doctor Within site it's most informative, he also advises against using anything with cascara sagrada in it as well which I am using at the moment but I have not got that condition and I'm aware of what can happen.

Has anybody got any helpful hints with bowel cleansing and colitis?

Thanks for any help, in the meantime I will continue to ravage this web site and any other I can find for any infomation.