Her brother seemed to think there was a possibility in that scene, and I seem to remember an implication that they moved to that apartment after an event something like her later outburst/tantrum. Given the at least perceived prevalence of youth suicide in Japan it doesn't seem unlikely the possibility is implied there.
Well, that might be true, actually. Mostly, I thought Kazama's brother wouldn't react like he did if there was a previous suicide attempt (just smiling and asking her if she wants to move) but he might just be relieved.that he didn't have anything to worry about.
I read the manga like 5 times now and didn't catch any suicide implications but I'm really prone to missing details so you're probably right.
I was flipping through the licensed copy I bought today (ok well I only bought Volume 2 because that's all they had) and one of the early chapters shows Kazama crying loudly on the balcony and then her brother runs over to grab her because he "was afraid she would fall"
so it's chapter 20 "Her Stumbling Block"
the scanlated version and the licensed version do have some differences in the text so that might explain the ambiguity here.