I wrote a lot about Gwyneth/Trisha when I rewatched the whole story in COVID 2020 - god knows what pages those are in this thread. My take was something I think Gwyneth echoes onscreen when talking to Steffi during the big reveal; sometimes she knows it's her, sometimes she doesn't. She clearly has a lot of rage and fury against Trisha as well as a lot of self-loathing, and yes, a lot of her dialogue with Clay, Jeremy, etc. early on in the story suggest someone who is trying to exonerate Curtis or others, or incriminate herself. (She keeps pleading with Alex and other members of the Corinth PD to look at her psych profile of the killer, and she tells Clay flat-out 'Curtis didn't kill Stacey' in a very ominous scene.) She also repeatedly breaks down and pleads for the killer to take her instead. Then there's the incredible scene with Neal in prison where they both know and are talking around it. But there are hints there in her scenes with her loved ones from the very beginning, even if IIRC Tudor wasn't told until late in the day.