I am basing my answer on a Google translation of what you wrote. Apologies if that was incorrect.
'She ate a chicken' means that she ate an entire chicken. The whole thing, not just some of it.
I don't think it does mean or imply that it was an uncooked chicken. That is possible, but would depend on context.
If 'she' was a dog or a ferret, then it is likely the chicken was alive, and raw. If she was a person, then probably not.