Yeah, it's not like Marietta said "fine Cho, I will do this for you" and pretended to like it. She glared at Cho the entire time. I have a whole headcanon where Cho herself realizes this, and eventually distances herself from Marietta. In the same headcanon, I acknowledge that Cho was dealing with a lot of trauma and not... totally "home" during OoTP, either. Very similar to Harry, actually. There's actually a really interesting parallel between them where Cho's response is to be all emotional and sad, and Harry's is to be angry.

The only thing I didn't like about the movie twist is that we then never see Harry acknowledge the difference TO Cho.

I've seen some fans say that they disliked her more when they were younger, so that might have something to do with it as well. But I also wonder if it's not more that people who don't like Dawn are very strong about it, so it's not as universal of an opinion as it seems?