Yes, I understood the part about the initial estimate...
Which I felt was probably about right...
And then the customer added on a slew of stuff after the fact.
I get that, and now that I've had some sleep I also get that in my example with the $600 tires I never added nothing in ways of "hey can you change the transmission too" and then acted shocked when I got a high repair bill, either... But I also think you have to instantly tack on those extras they like to throw in, right when they're doing it you need to let them know it's going to cost more and how much, right then and there, not wait until the end.
Granted a piece of me likes to think this customer knew what they were doing all along but we lack the burden of proof and one hates to take even the smallest leap towards a conclusion out of fear of jumping the gun... I just don't like doing that, when we don't know.
Have you tried talking to her, explained to her that it was all those extras (and feel free to name them off one by one, explicitly by name) she added to the job, for example this wanting this done this way costed another $40, then this over here you wanted that done which tacked on another $30... And so on, piece by piece line it out for her, might even have to sit down with the customer over it.
There might be some reasoning, yet.
I'd like to at least try, if for no other reason we can say you did.
Might try that, may have to compromise some...