If all she wanted was a friend, why did she avoid going to school... for one hundred years...?
Also, she if he's a homebody, she seems pretty social, and quite open with the MC so far, so it doesn't seem like she's socially deficient, so why skip school and (seemingly) stay at home locked away from everyone?
You might say it's because she's scared of other people, due to her previous experiences of being excluded, but again, she doesn't act like that's the issue.
Also, I wonder what her one hundred years worth of handouts looks like - does she also have to catch up on all that homework?
