Hullo Lily, I am Emmie! I play four characters and though none of them are Hufflepuffs, it looks like there's a chance that there still might be some interaction.
Michael: He is fairly good friends with Justin (and kinda Ernie) and y'know, the DA in general so there is a possibility that they could know one another pretty well. And he dated Cho so if she was friendly with Cho through Cedric then he might have known her through that avenue as well so I could see this being the most definite option. Michael gets on well with Justin and he usually gets on with Ernie though they can butt heads sometimes so yeah. We can chat about how Mikey and Shiv get on.
Marietta: She is Cho's best mate and was also pretty well known to Cedric because of this (and because of Zacharias) so if Shiv was close to Cedric then it's fairly certain that she had to deal with Marietta at some point. This may or may not have been unpleasant for her. Lol. Marietta has been nice around those people for the most part but she was showing some nastiness every now and again when Cho wasn't around (especially when she dated Michael because Michael drove her crazy) so there's a chance Shiv could have seen some of the little outbursts.
Ron: While Ron is involved with Ernie and Justin and Michael through the DA, other than that he's not like, BFFs with them so I'm not sure that he and Shiv would necessarily have much interaction as far as friendships go. But randomness is always fun and Ron is an Auror so who knows, they may end up doing something eventually!
Samara: Samara is probably the least likely to interact with her, unless she happened to be at Azkaban when her father in law was there, which was around the end of the war. She was in Slytherin and an Obliviator and is going back here in a couple of days. She married to Elijah Chambers who is an Unspeakable and they have a son who is five. They are super creepy, just fyi, and tend to stop at nothing to get results (like killing people and experimenting on their friends without asking).