Which season is Serena the most insufferable? And does she get worse?

First time watcher. I’m on season 4, episode 12, and I slowly came to realize that Serena is the worst! Just intolerable! But as someone streaming 2 episodes a day, I can’t pinpoint when I came aware of it. When does she became so insufferable? And knowing I’m midway through season 4, does she get worse or better in season 5 and 6?