Well, Maria definitely sounds like a reincarnator. She might have thought that acting "nice" (being pushy) to Rururia was enough to set the "best friend" flag and have her lie for her in the condemnation event or similar. Rururia was busy with not flunking so she didn't pay attention. Meanwhile, Sara seems to have something to hide and likes being friends with Rururia because she's so oblivious.
I'm still not sure about Irene. The way she's surrounded by men makes it seem as if she is another reincarnator also going down the reverse harem route (reincarnated villainess maybe), but her reaction this chapter shows her being troubled by their attention. It might be that she is somewhat like Katarina, in that while trying to avoid her own death flags she ended up making the capture targets fall for her, but she isn't actually interested or trying to do it. Kind of how Rururia herself caught the interest of the king's brother by just being a reasonable person. If so, it might be that she honestly wants to make female friends of her own age, but can't because of the men surrounding her.
I hope that's the case, because then she can join the group of people that complain to Rururia about their problems.