Usually pooping and peeing on the bed is either marking, OR a medical incontinence issue….But, not an actual housetraining problem.
Bella is probably feeling comfortable enough in her new home to claim some important spots as "hers"...that doesn't necessarily mean she is challenging YOU...but it means she is letting all other comers know...this space has been marked.
For now, don't let her go into the bedrooms unsupervised AT ALL. If she goes in you must follow her, and watch her like a hawk...if she makes any attempt to eliminate...shriek!!! No! Yuck! Aacck...whatever it takes so she thinks "wow...mom really hates that...I clearly am not supposed to do that"...and you take her immediately out of the room, outside, into a crate whatever...needs to be black and white...this happens you are out!
Is there any chance that she was awake and trying to give you some signals she needed to go out before she peed on the bed while you were in it? I can see her saying 'well, I tried to tell them, but they won't wake up...I bet this will wake them up'
When you are at others people's homes, I would keep her on a leash, and under supervision at all times.
This behavior is likely to pass as she realizes she doesn't need to mark everything to keep her safe and secure. But in the meantime, don't give her the chance to do it.
Good luck! I hope some of this helps....