If you don't understand Connie's reaction, I think you're stuck in Steven POV. Because if you look at the situation with Connie's eyes, her reaction is much more logical and coherent this way. We're in this weird moment where they don't get each other feeling, and I think that since we see everything through the eyes of Steven, some people don't understand why Connie is acting this way.
In my opinion, her reaction is realistic, and really better than just "I'm happy that Steven is back that's cool let's act like nothing happened". It makes her a much more interesting and complex character. So, calling her the worst character for that just seems... wrong. And salty because she doesn't get Steven's POV and consequently our's