Both my kids were nightmares to potty train. I feel you :( Idk if advice is helpful but:
One thing that helped was gentle, non-toxic shame. Not punishment or berating them, just a nonemotional "well I guess we have to buy diapers if you're not going to use the potty." It's just objective fact. Babies wear diapers because babies shit their pants...whatever, be a baby, but you gotta wear a diaper. Once it's not a "thing" to you it's not as much fun to fuck with you about it. (fucking kids lol)
Another thing that worked for my 4 year old son was this potty training"advent calendar" thing. He really liked getting to pee/poop on the potty to get a new toy each time.
You're being very kind and we don't know OP, but sometimes it's more severe though and the parents really do need therapy.
Second born children are what professionals call "spirited." This
unique grouping of children have the potential to ruin you mentally,
emotionally, spiritually and financially. Here are some tried and true
tips for keeping that second born of yours out of the US prison system
and time out and into something that doesn't involve fire. "
​
https://www.amazon.com/Second-Born-Lunatics-Keeping-Prison/dp/0990592847
Get an easier one. I had this one and loved it. You put it on like a backpack in the front, click one thing around your waist and put the baby in, super easy. Carrier
Some of the wraps are so complicated, I would have dropped my kid for sure hahaha
Can you put a lock like this one at the top of doors, where only you and other adults can reach. Lock her out of the rooms you don't want her to go in. I don't know about locking a 3-year-old in a room, that is 100% your choice as parents, but maybe keeping her out of as many rooms as possible will help?
Read the Amazon reviews on toddler bed safety nets, some of them are very humorous. My 3 year old daughter thinks her "tent" is really neat, like her personal cocoon. When she gets restless at night she eventually soothes herself back to sleep. I found that going in there constantly was just stimulating her every time. https://smile.amazon.com/RUNNZER-Baby-Safety-Canopy-Climbing/dp/B08NJGZQZM
I read your original post, but haven't read the comments.
That thing about the baby needing to sleep on you...maybe something like this would help:
https://www.amazon.com/Tranquilo-Mat-Portable-Soothing-Vibrating/dp/B06W9FJ31Y
I don't know which item of this type would be best, though. You'll have to do the research.
Good luck! Better days ahead!