Michael: Oh sorry, I didn't mean that she was in the DA, I just meant that Michael hangs out with all the DA people which include a lot of Hufflepuffs so that's how he could know her.
Marietta: Well it's not frustration so much as Marietta is a huge bitch. She's currently the first minion of Pandora. :) Her and Cho's friendship is falling apart because of it, so yeah. But she was usually pretty nice around Cho but it was fake and Cho is finding that out now.
Ron: He is always up for trying to help rescue people!