I mean to think about it in her childhood she never used transform, she only drank others blood and her parents knew it was quirk related. And then for what I assume is the next ten years of her life she never uses it. We don't see her transform when she drinks her crush's blood when she snaps.

Did Himiko just think her quirk was cannibalistic urges and thoughts. I wouldn't suspect her to have any actual consoling over this as a child based on her flashbacks.

Do you think the first time she actually used her quirk it was while she was running from the police scared for her life because she just committed a crime and shes been called a demon since she was young and people like do away with demons? Do you think she was hiding behind a backalley crying before using her quirk for the first time and turning into this person she just drank to blood of because the police were going to find her and they were going to take her away and she was scared and she was only fifteen?

Can you think of how scary that must've been for her body to suddenly change around her, for her own voice to change for her height to change for her body to not be here anymore?