I actually watch this show (have to watch the Japanese version to keep up to date). The TLDR of what happened (what caused the bullying) goes something like:
* Goes on a trips w/some of the housemates which is kinda of a double date at the same time.
* Kai (dude she was going with) was out of it, struggling w/money, and thus was anti-social the entire trips (he probably shouldn't have gone).
* This angers her so she and the other girls on the house kind of start pressing him to leave by questioning why he's even there if he acted like he did (this is done in a petty, mean way).
* Kai accidentally washes her wresting outfit due to not checking if the washer/dryer were empty before starting a load
* She EXPLODES on him, he feels bad an apologies, leaves the house.
Most fans of the show felt she acted like a child when she lost. Kai definitely wasn't in the "right" but her reaction was FAR beyond warranted, esp against someone who was also CLEARLY struggling with mental illness himself. Both needed help and neither got it. Sadly for Hana, the internet can be a vindictive, shitty place.
Also worth pointing out, due to COVID-19 she was essentially out of work. She still collects some form of a minimum wage salary (as revealed on the most recent episode), but most of her income came as a % of sales of tickets + merchandise from shows, so this could've impacted her on top of the bullying.
RIP Hana