Doesn't really matter what they do or don't, you can't go invading people's privacy just because, for whatever reason, they're not going out of their way to try and keep you out. That IS absolutely her fault.
No reason to let her get in the room or in the sleepover considering it's very obvious she still has lots of interest in Fumi.
They just had to reject her and they didn't.
I get what you're saying, however, there are people, even in reality, who are too shy to be upfront with others. It could be their case that they can only be upfront with each other, but still can't really deal with other people. On top of that, it doesn't really matter that they ended up "inviting" her later on, because she had already pushed herself on them...
Edit: Also, reading the other comments, it occurred to me that in manga there seem to be this trend of respecting elders, probably also the case in reality, but don't quote me on that. Add that to everything else I said and you got yourself an airhead, a kinda pushover who just wants to make the airhead happy, and an annoyance.
last edited at Aug 15, 2017 5:10PM