James was a bully in school — to the point that even the biggest of James Potter apologists can't deny this. He mercilessly teased Snape, and in one particularly horrific memory, hung him upside down and exposed him in front of the entire school.
Cho was not fond of Ron Weasley and Hermione Granger however; she did not trust Harry's closeness and friendship with Hermione, generally suspicious that Harry had feelings for her as well. This was one of the reasons that Cho and Harry fell apart.