What I can't fathom is that someone would idealize mid-noughties channer retardation.
In and around nerd spaces, such as imageboards, you quite often find people who were gifted as children, and were praised and treated as special by adults for things they did without effort. But as they grew, they didn't put in effort to channel their abilities into schoolwork or a career.
Bella strikes me as potentially in this category. And if she sees herself within this category, then it makes sense that she would strive to be a notorious and/or special example of this category.
I think the logic is - if I can't get lots of attention for something, then what's the point in putting effort into it?
Her bad hygiene can be explained by this logic. People with ADHD and/or autism have to put in more effort than normal people to maintain normal hygiene, because they get distracted, don't like transitions, and they often have sensory issues with clothes (which is why they wear the same clothes).
Also, I think Bella has body-focused repetitive behaviour disorder. The pocks on her face may be the result of skin-picking (excoriation disorder), and in the photos of her feet, her other toes are bloody, leading me to suspect that she picks at them (onychotillomania.) Picking at her toes repeatedly would allow fungal spores to get in over time.
So, for Bella, the choice she faced was - put in effort to not get hygiene-shamed, or put in zero effort and get attention/be special (be especially unhygienic.)