With Filou it helped to change from a closed litterbox to an open litterbox. Now -more litter on the bathroom floor but no more pee outside.

I would try another litter.
And get rid of that couch. I guess it is now so litterbox-like for her that there is no chance to get her away from it.

If it is not an UTI or something different, it can be a very complex thing.

Good luck and don't give up. I agree with Laila: cats are complex.