Apple TV+ series “Bad Sisters” is part comedy and part thriller — following a group of sisters who may or may not have killed their toxic brother-in-law. “I had finished ‘Catastrophe,’” Horgan, 52, told The Post, referring to the previous show in which she starred and co-wrote (2015-2019).“That was a big part of my life for four years, writing that with Rob Delaney and making it. And when that ended, I had to look for something else. They’re quite big shoes to fill – you’ve got to love it, because it’s an awful lot of work.