Well, can't answer for Yellowglow exactly but I bet it has something to do with Ai always acting snotty and bratty. (Conan does note this frequently.) She's also kind of vain... I personally like Ai as a character, but I like Ran better. She's nicer, kinder, braver, sweeter, more trustworthy, strong but with weakness, patient, funny, dependable, and just plain old better. That's why she should go with Shinichi!