Just dont get her
She's counting on that.
Im the most normal person in her life as a man. Her other bfs were a.sholes. Beating, cheating, trying to kill her etc etc.
Which is what she wants (but maybe with you as a safe emotional cushion).
I guess she bored with me because
you don't beat her, cheat on her, try to kill her etc that's what she wants, just accept that you can't fix her and move on. And I really, really, really doubt that this started only after three years.
You're not the first guy to fall into the Captain Save-a-ho trap and you won't be the last. But she doesn't see you as anything but as fallback and is incapable of devotion to any man who doesn't treat her like sh1t.
Walk. Away. Remember the warning signs so you don't get played again.
Stay frosty, as they say. Stay. Frosty.