I think its about trying hard, putting everything you have into a relationship, only to learn that everything you built it on was false, that even though we get hurt we keep coming back for more. Because we're human and we crave familiarity, we end up hurt. It's about wanting to be irresponsible for once, wanting someones else to be the one that everything gets put on. Because if your not responsible, the blame won't fall on you. She's sick of it but she can't get out, cause he's home.
Then again maybe they're breaking up or shes getting revenge aka "Settling the final score."