I imagine Ibuki coming from quite an average middle-class family. And I feel that her FTEs point toward her being an only child ("one-person tag and one-person hide and seek"). I can't decide, however...
Whether her parents are artistic types, or she's an outlier/black sheep
Whether her parents encouraged her to pursue music
How her parents felt about the breakup of her light music club/her new artistic direction
But I basically don't think her despair originated with her home life in any way. I find it very touching if Ibuki lost her optimism solely due to rejection by her former bandmates > a negative and even cruel public reception to her solo music (I'm just extrapolating from her classmates' reaction to it in Ch. 3) > becoming a public laughingstock > fearing her audience, developing paralyzing stage fright. If the world just didn't seem to have room in it for her. A lot of her classmates basically never had a chance to live happy, fulfilling lives; the way they were raised precluded it. But we have no reason to believe that this was the case for Ibuki. It just so happened that she reached the age when a person starts to step out into the world, and the world rejected her.
...I love that SDR2 in particular encourages us to overthink these simple archetypes, because it's fun to imagine how they came to join a murder cult.