In my view this manga is mostly trying to make fun of overly dramatic girls that do anything for attention and call themselves mentally unstable.
Take it with a grain of salt or just don't take it at all
google Borderline Syndrome
I think, this is girl is mentally unstable even a disorder, but not quite there. To be diagnosed as a disorder is when you are a danger to yourself or others. Cannot function socially, work, and school. Can't keep up with your daily must do's like eating, hygiene etc. AND etc. There are a lot of people who suffers from anxiety and yup there are cases like this one. It could be that they have a tendency (Dependent Personality Disorder) but there's just no one pd nowadays some relates and connects with other disorders. What I'm trying to say is while this is annoying (to borrow your words) I don't get offended by it. I just read it. And it does show that she is supported (As we can read from the brother's POV) which is a big plus in overcoming disorders.
I don't really know the purpose of this, maybe to spread awareness? Or I don't know it doesn't have to have a reason just that the author wrote it.
I think I get now what you mean, do you mean that this is just written too lightly and mental disorders shouldn't be treated like that? If that so, I get you. But, let's see on the flip side of things. Mental disorder can be a heavy subject if discussed correctly. But, I assume a lot of people is going to crack their hands in their keyboards if it is written/drawn so explicitly. It's not a pretty sight. It's the truth but I remembered when there was this case of something that was popularized (I don't know if it was suicide or dissociative identity disorder) there was an increase of people that did it or was diagnosed with it.
So how can we thread the line in making the public aware? How to do it just right? I respect that you got offended by it. Maybe, the sister overcomes this? Or maybe we will get to see how support from your family, from all around you make you overcome things. I dunno maybe both.
The term menhera actually comes from Mental Health (men from mental and hera from herafu) it was actually some campaign from the japan government or smth but it became a slang, and now it's used to describe... well... i guess ppl like menhera chan, cute but depressed and anxiety driven people. So this whole thing is alrd a 'joke' from the start.
Omg I hate how this ‘Mentally unstable’ is portrayed. Threatening with suicide, telling others you will kill yourself and just randomly putting a knife to your arm in public because someone doesn’t agree to lie to you feels toxic, not mentally ill or unstable. Not even bipolar would explain this. As someone with mental illness, and similar scenarios to the story I think it is a bit annoying maybe even slightly offensive to read this manga.