Cho Chang at Hogwarts an extra year?

I was just thinking after 阅读 Prisoner of Azkaban (again) that Cho Chang is a 年 older than Harry, right?

But in Deathly Hallows when Harry, Ron and Hermoine come back to Hogwarts, Cho is still attending, -she's mentioned and even has dialogue, while inside Hogwarts- even though Harry is in his final 年 (Well he dropped, out but he WOULD of been in his final year...)

Cho would have sort-of moved on...?