For me, my dislike of her comes much more from the attitude she gives off.
Outside of her interactions with Data, she's brusque, domineering and frankly unprofessional.
Her attitude towards Data is bigotry pure and simple (and the kind of bigotry we'd not expect of a senior medical officer serving on Starfleet; and was largely settled in Measure of a Man... but we won't talk about that episode, its an entirely different rant.)
Lets just put it this way. If any of my employees said the same kinda shit about another of my employees, they'd be terminated at my earliest convenience. If they did that to one of their superiors? (remember, Data was the second officer. In terms of shipwide command it went Picard->Ryker->Data.)
More to the point, she was constantly manipulating him into shitty little games goading him into proving his capabilities as a person. Like in the Moriarty episode, and in the episode with the strategema guy. (the battle simulation with ryker and a small contingent posing as a disadvantaged opposition,)
To be fair a lot of the problems with the character stem more from the fact they wanted a heel than from anything else. she didn't grow into something tolerable because they didn't want a character that grew into something tolerable.