I also think she got tired of the s***, certainly there are other reasons listed, for example people say she wasn't used a schedule of a main character for the show and that she didn't like Toronto. I think this is stated to deflect some of the other things.
I have found that I can't watch too many of CW's shows. I did try to watch Crisis but kept forgetting when it was on and only saw a couple of episodes.
All the angst in practically all of their shows drives me away, pretty quickly since it seems to be a staple element in just about all of their shows. I tried to like Riverdale, Arrow (I was gone after season2, Oliver was too broody for me.), Nancy Drew (there shouldn't be angst in this show but there is), Batwoman (went right to the angst well in episode 1), Supergirl (I stopped with Kara/Jimmy Olson drama). I could go on but, you get the idea.
It's like they took the Smallville thing and try to re-create that thing but upped the angst.