Relationships At School Start On Lies - Tumblr Posts
I don't know if anyone's already mentioned this, but I feel sorry for Haruhi. Like, I know she got into Ouran highschool on a scholarship and is already isolated from her peers by the fact that her social standing is so far below them, (as well as not being able to afford what they can, obviously) but the fact that Ouran has a middle school and most likely a primary school, so it's a K-12 school means that everyone realistically already knows each other.
So even if she wants to make friends outside of the hosts, it would be hard to break into the friend groups which have been together for literal years and through so much, adding to her isolation. Which makes sense why only new kids and the host club are her friends at the school, as she, Ritsu, and Renge (in the anime, at least) are close and know her secret, and are the only two other new kids shown in the anime.
Because of this, Haruhi probably felt exhausted even if she tried to make new friends, as everyone has most likely known each other since birth, and she has no connects other than the club.