Did the same guy destroy her secret base when she was a child and what she had now?
Peak awkward when she got together with an ex boyfriend who trashed her childhood base and her base now
He assumed it was her ex, but there's been no confirmation on her side that I could find.
Given it's likely the same person destroyed the childhood secret base
and then her home in the present, coupled with the fact she called him by his first name (and he used hers), my guess is it might be an older brother who's just a moocher/lowlife trying to strongarm her for money, and has always been violent and delinquent-like.
Plus, it'd be extra weird if this guy was an ex-boyfriend, since the base was trashed when she was like in elementary school. Sure, it's not completely impossible some kid in her class did the deed back then, and she ended up dating him later on or something, but that feels like a way bigger leap (and more narratively convoluted) than him simply being her brother.