Did it ever occur to you that the reason for that is that Sugar made it far enough into the game to have to backstab her allies and Corinne didn't? Had it been the onions who ran the game after the merge, they would have had to backstab each other too, and rest assured, they would not be as tight-knit as they are now.
The last part is true - but you should likewise admit that most allainces that won 6.\7 ICs and then got screwed in a twist would be somewhat bitter.

Sugar was unpopular from the get-go on Koror because she cried a lot, wasn't very useful, and especially because she alligned with Ace. The rest of Kota wanted nothing to do with Ace alliance-wise. So ironically she opened with the same mistake she accuses Charlie of, alligning with "bad people" making her just as bad. If Charlie is responsible for Randy and Corinne, she must take blame for everything Ace did.

And her booting Ace was still a dumb move made after the damage had been done.