Female cats are difficult with toilet. If there is poop in the tray, they pee on rugs, blankets and, children's beds.
There are two options:
1. have at least two trays, three maybe even better, two of them should be silica based, as this occludes the pee smell better, and bentonite and similar clays are best for hiding poop smells.
2. let her go outside whenever she wants and she'll always search out a clean spot to pee.
We've tried different litter and multiple litter boxes and cleaned them every day.
Not saying you didn't do everything you could, I know what it's like, I had a little cutie that did this and it was an epic moment when I woke up hung over and she was crying to be let out so she didn't have to pee in the corner, and I clocked her right between the eyes and she shunned me for 3 days.
I stopped locking her in after that, and the problem went away.
If that's not possible, and you can't exclude her from the boy's bedroom effectively, then you need to send her away. I presume that you live in an apartment. I just moved into one, and I don't want to torture a cat by trying to contain it in here, it's basically impossible to contain cats without having problems.
I lost a pretty white and black cat in 2018 because he kept on sneaking outside my top floor apartment and most likely pissed off a negihbour by frequently breaking into their apartment through an open window, I never saw him again after one day.
Cats are not easy to keep if you don't live on ground level or live near a main road. Nothing worse than that moment you realise they have disappeared.
The other alternative is to be really strict at controlling her inputs of water and wet food. If you only feed her once a day, and don't leave dry food out (shame on you if you feed a cat grain based food anyway) you can predict when she will need the toilet and make sure you double and triple check her trays to make sure at least one has no poop in it.
If it was a neutered male you wouldn't have this problem, so long as he never got nervous while young and wasn't neutered early enough, that he started spraying.
If you think female cats peeing on blankets is bad, you should see what it's like when boy cats are nervous, usually due to dogs, other male cats or people who torment them, their pee smells WAY worse than female pee.
