I agree with Ibsgrl, you didn't do anything wrong, it just sounds like another idiot GI who's not taking things seriously. I think you've mentioned this before, but how old is your daughter? I would try and get a referral to another GI, because like Ibsgrl said, you just can't be diagnosed with IBS without ruling out other things. I was told I had IBS when I was really young (about 11 I believe) and now I'm really sick and have been having a lot of problems, and I'm just now getting some doctors to take me seriously...you really have to fight to get the care you deserve.
Your daughter is lucky to have such a great mom! Kelly