Potty Problems

So we finally brought Paisley, our new cat home. She and Chewie didn't exactly get along, but I think they're gonna be okay, they've made a lot of progress.

But here's an unexpected problem, she's about two years old, they think, and she's been "litter box trained." But when we brought her home, she has now peed or pooped on every bed. And she likes to use the floor too.

Every time we let her out of her room, she rushes somewhere else to go to do her business. We have to keep her in a room with her food and her litter box whenever we leave the house because every time we come back she's made a mess somewhere else.

My mom is really upset by now and looking at sending her back to the shelter if we can't get it under control soon.

I need help, I don't want to lose this little sweet heart!

How can I re-train her not to use furniture (mainly beds) and to use her box instead. It's like she was trained to use beds, it's almost engraved in her memory that she's supposed to use a bed.

PLEASE HELP!!! Thanks a million!!!  

First, you have to thoroughly clean (and maybe more than once) every area where she has peed/pooped.
There are several articles about litter boxes--placement, how many, how to clean.
Do you know what litter she was using and what kind of box?
And how many litter boxes do you have? The normal ratio is: one litter box for every cat, plus one. Which makes three in your case I think.
Good luck!