@tae_ka_pre she couldn’t be Utaha. She’s literally an awkward unsocial girl who thought the best way to thank him was through what she overheard from others. She straight up says she does not know how to express to him genuine thanks for helping her this much, and that’s the best she can understand to do. Becoming his phone fuck buddy is a big assumption on her part but she’s a doofus so it doesn’t seem too out of the way. I mean, it’s weird but I won’t question it since she was always proud of her body and thought men would desire her without question or want a relationship with her.
But if she started acting as a teasing queen of seduction like Utaha I’d be way more surprised at that since she never showed any sort of characteristic like that before. Utaha understands MC a lot and is way more comfortable around him. This girl on the other hand is only capable of throwing assumptions around and barely understands people in general so again, while her behavior isn’t what we consider anywhere near the norm, it definitely won’t make more sense for her to act like Utaha.
To me it just shows once again this girls actions are having a negative effect on MC by acting however she wants but at the same time surely there is development in the right direction.