I always thought that was an unfair classification of her character since you can count the episodes on one hand in which her feelings for Spock are addressed. "The Naked Time," "Amok Time," "A Private Little War," and "Plato's Stepchildren." I don't count "Journey to Babel" and "Return to Tomorrow" because there isn't anything there that makes Chapel's feelings for Spock obvious in those episodes (but the shipper in me squeals in delight when I watch these episodes). Most of the time she is a highly efficient officer and Kirk, Spock, and McCoy clearly trust her like in "The Enterprise Incident" she is one of the few people to know the whole plan.
"Throwing herself at Spock in 'The Naked Time'" is always the accusation that grates on my nerves because there is such a double standard there. I don't think she can be blamed for anything in "The Naked Time" unless we want to hate on Spock for crying about his mother too.
I don't want to get too into my opinions here because I want to hear from you too.
For more Chapel insight the writers' guide speaks very highly of her, and here is an excellent essay from the '70s. (I think many of you might have already read it) Yes! Chapel hate before the new movie, even before ST: TMP.