afaik thats basically it. I think it means 'sickly cute', like a style/aesthetic that gets inspiration from mental illness.
It's technically supposed to be for raising awareness and public acceptance, but that side is mostly ignored in favour of menhera as a type of anime girl personality. Think clingy but in a cute way, anxious but in a cute way, sad but in a cute way, etc.
I guess some people (including OP) even find it attractive? idk anything about SuicideGirls though