Lean more into Sadako's theme as a confusing, hard to track killer
As Sadako plays right now, it seems like the developers were going for a killer that is hard to track and hits survivors off that confusion it generates, since she can be anywhere on the map.
I think that you can make small, incremental changes to her power level to make her a strong(er) killer on release, without breaking her or making her unfun to play against (alla Blight).
The best way to do this is to lean into this theme you centered her around.
Make her condemn feel more pressing and terrifying. This can be done by creating illusions that gradually increase with each level of condemn. At the first level, maybe make her randomly appear on a survivors screen, similar to doctor. Then at second level, make her crawl out of TVs near the survivor, which will make them second guess if it's the real one or not. At third level, she might walk towards the survivor in demanifested form, etc. This would create a lot of fear and confusion around her and make it so that the real Sadako could get first hits more easily off this (, since she is easily looped). Maybe even make survivors breathe harder when they hit a certain level, so they're more easily tracked and/or cannot play stealthy when they start getting up in bars (, meaning that Sadako will get in chase more often since she can location people more easily).
Make holding a tape more punishing. Don't do this by simply speeding up the condemn bar, but rather making it so that you feel an urgency to return the tapes (, which you don't get on lives). Make it so that the survivors are slowed by 1-3% when holding a tape, so if they get chased while holding one- they will go down more easily (, which can act as like a situational looping power for Sadako). Also, make it so that their screen gradually gets more and more dim/the edges get blurred out and/or darkened, similar to how a screen gets dark and blood when you don't mend for a while.
Make Sadako not have a huge cooldown on her M1 when she taps de/manifestation. There is no zoning potential to clicking this ability. There can be a cooldown on when she can M1 after trying to (de)manifest, but it's way too long on the PTB right now. Just lessen it a bit. Her looping is already trash, she doesn't need more shackles on it.
I think all these changes would make her a much more fun and unique killer to play as and against, without shifting too much power into her kit that she becomes an overpowered mess. It would also make it easier to balance her, since there would be more elements to tone up/down. I think the base kit is great because of how unique she is, but there is just a lot that is left feeling lackluster (because it isn't thought out enough, maybe?). As it stands, survivors can cleanse condemn status too quickly and it doesn't build up fast or create an urgency to get it off, similar to Pig (, which is already an agreed upon weakness of her). It's also slightly RNG/not consistent enough.