Has anything you have tried to say to her ever got through ?
Other than your frustration and bust ups, what have been the fruits of trying to broach the subject of her management of her financial situation ?
If all you are getting is heartache and fighting, without any compensation in the form of helping her find a better way to budget, then stop.
Hide her on facebook (I think you can do that rather than defriend right ?), if she starts to whinge about money, change the subject, or find a reason to leave the room\end the call (go for an unneeded, but convenient cup of tea, a pee, popping to the shops). worst case scenario and you can't get a way, listen rather than speak, with the occasional non committal "ah ha" to demonstrate your presence int he conversation. (very good idea to think soothing thoughts at that juncture, to avoid boiling over with frustration)
Sometimes you just have to accept that people need to find their own way (or stay lost) and you cannot make a difference over and above creating bad feeling that they then use to deflect their attention away from the self induced nature of their plight.
Be there if you can if it all goes horribly,horribly bent, but don't let anybody take the piss by using you as a constant money shaped crutch so they can avoid facing up to the results of their behaviors.
The above is where nobody can take away your control because those are your choices and yours alone. Feeling back in control again is a huge relief after a long period of feeling impotent.
Possibly opting out of the dynamic where she uses your (perceived) criticism as a distraction, she might reflect on what lies within her control a little more. If her frustrations with her situation cannot be redirected and released via a row with you, then maybe they will build to a critical point where she reassesses how she wants to go forward. If she is free from external criticism she might be less defensive, which helps when you need to be a bit more self critical.
I don't doubt that your motivation to challenge her comes from love, but it might not just be "not working", it might actually be thwarting any progress, and it is upsetting both of you to boot.
Time to try something different, and I can heartily recommend the sense of liberation that comes from accepting that which you cannot change and focusing instead on solely the choices you have complete control over. Your own.
I know it is easy to say and hard to do. I stumbled so many times, mainly out of a sense of guilt from not trying to solve their problems for them by poiting out they needed to deal with the heart of the matter, but it was really worth the effort to get there in the end.