No not psycho, but mentally questionable. I've got a female friend, an identical twin like Cat who voiced an interesting theory. Her opinion is Cat is so intent on differentiating herself from her identical sister that it over rides her basic judgment. She too is a Big Brother watcher and sees elements of her twin sister in Cat. I can't quote what she said verbatim but it was along the lines of growing up and never being the singular, always being associated with a sibling despite the context.
It's amateur psychology but it gave me a sliver of insight I'd have otherwise looked. TBH Cats sister when interviewed was not exactly overwhelmingly complementary of Cat. In the letter writing task, it was interesting Cat chose to wrote to her. Cats sister is possibly the slightly smarter, slightly funnier, slightly more attractive twin. In that light, making such questionable decisions in regard to her personal life become more understandable. I believe decisions Cat makes in her own life involve a number of factors, as they do for all of us, but one of them is "What would SHE do?". That's not an issue for damn near all of the rest of us.
As for Lawson there is clearly some sort of emotional baggage associated with his mothers death. Maybe his outside girlfriend is reminding him of difficult period in his life he wants to leave behind? Maybe he has grown apart from his girlfriend but can't bring himself to break up with her because of how her and her family looked after him during a difficult time? Maybe Lawsons reactions around his mothers death have given him a false guilt complex?
Who fucken knows really? Judging from the footage I've seen, Lawson is a follower not a leader. Someone who's more eager to please than worrying about pleasing himself. The hotel task revealed Sam and Ryans thoughts about him. The guests group described him as a "water carrier" The footage being what it is, I'm yet to see him stop a housemate and disagree with them about a viewpoint.