Some real people just don't wanna see their special pretend people behave this or that way... All I can say is that I'm sorry. Characters serve the story, not the other way around.
Yeah, they can too. The existence of complex plots in the halls of fame don't wipe the simple ones from there.
The structure and pace of the plot is very deliberate: Joel is randomly killed by a group of strangers out of the blue. This is there to put you into Ellie's mindset: if you were expecting to spend time with Joel (or even play as him) that is denied to the player as it is denied to Ellie.
That pretty quickly gets you hating on Abby. So you're all onboard with Ellie getting on a horse and heading for Seattle to help Tommy kill those responsible. Then, during the game's first climax, the game pulls back and says: wanna hear the other side?
You see, this huge woman who killed your beloved character was the daughter of the surgeon Joel killed. She loved her father, looked up to him, loved what he loved (collecting coins, caring for animals, etc...) and wanted to spend the rest of his life with him. But Joel went and murdered him to prevent him from saving mankind. So she has a grudge, just like Ellie has a grudge against Abby now. So, just like Ellie did coming to Seattle, she spent years preparing and looking for Joel to exact revenge.
And now, just as Joel's past caught up with him, Abby's past is catching up with her.
The plot's structure and pacing are deliberate here in order to make you understand there's two sides to every conflict. But they don't just want to tell you that, they want you to experience the both sides.