Personally I came to hate Irisu after what she did. By tricking Oreki she shattered a fragile sense of self-worth he was starting to develop. Even if it was to help her friend, I find her actions deplorable.
Wasn't it because she didn't really care much for her friend's story to begin with but didn't want to say it sucked, so she forcefully recruited Oreki, tricked him into writing the ending, so that she would look like she helped her friend?