There's a few things here OP.
Occupational health should be involved in there is a pattern of absence related to the same health issue, and from your posts this is clearly a pattern. They can help with reasonable adjustments to get someone back to work/make their work-life easier.
There's every chance this is the first steps in managing your partner out. If I'm reading correctly and your partner is having multiple absences a month, this is making them hugely unreliable to the business, especially if they have any kind of responsibility to clients, projects or employees.
If they're being bullied as you say, they're not going to have a line manager fighting to keep them in the role either.
They need to tell someone the real reason they're taking time off. Have they mentioned it to their GP? OH involvement could lead to a request to see medical records/contact your partner's GP for info on their condition - at least they would have some backup/evidence should things come to a head.
Finally, not to add to your stress, but future employers can and do ask for information regarding absences. The previous employer won't disclose the reason for the absence, but will give info on the number of days/instances, and it's the instances that raise red flags.
If I had a reference for someone with repeated short absences over a long period, I couldn't take the risk. I completely understand why they haven't done so already, but I'd strongly advise your partner to get the bullying on record and look to resolve this rather than leaving it to get worse...as others have said, they could perhaps offer a move to a different department, which seems like it would have a huge impact.
Good luck ❤️