Did she live as a pet when she was a breeding bitch? If not, then she may not have learned how to act around the house. I would do as mentioned above. Move things up and out of her reach like you would with a puppy in the house. Also make sure she has chews and toys you can give her as an alternative to your things.
I remember reading that it takes around 4 months for a rehomed dog to really settle in and be comfortable enough to show their true personality. So maybe that's why she started doing it now, because she is really at home in your house and comfortable enough to explore more
Cockers do enjoy collecting things. My girl collects socks and leaves them randomly around the house. Found one outside yesterday. But she stopped chewing things when she grew up. If your dog never lived in a normal household, she may not have had a chance to learn some things and maybe you need to think of her like a puppy in some ways.
If she did live in a normal home then it could just be a bad habit. Either way I think moving things out of her reach and having chews to swap with when she does steal is the way to go to teach her.
Added: If she starts treating the stolen objects as puppies consider pseudopregnancy.