Sure, it would be a lot easier to resolve things if they just talked about it, but...
I can kind of understand where Hanamaru's coming from. She's scared of being rejected, so she'd rather have this halfway, awkward relationship and be unsure where they stand, over finding out that her feelings are one-sided and losing Yoshiko completely.
It's really easy to say "it'd be so easy for them to talk." Maybe it is, but it's also really easy to psych yourself out like what happens here.