I think the "Honey, this isn't my problem" is great. You don't have to sit there on the phone and listen to her complain about anyone and everyone, and most especially when she turns it on you. I also like that you said you were busy and had to go. Combine the two and I think it's a great way to let her know it's her problem and that you don't have time to listen to her complain. And, of course, telling her that you love her before hanging up is very important.
You're doing fine. Hang in there. We're always here for you.