How did we get here?

I have tried different things over the years, but we are heading into scary territory these days. We have come to a point where the child thinks she has the right to speak disrepectfully to her Daddy and me. She has taken to telling me absurd things like, "You just don't even care!" and, "You don't love me!"
At my wit's end, I mentioned it to my sister.
She is the queen of inventive solutions to correcting kids.
Her suggestion was brilliant. (of course)
Every day (or other day, or week, or whatever time frame works) assign her to write down ways that I have shown love and caring.
And while she was at it, I was to do the same thing.
I'm looking forward to sharing our lists later today.

This morning, after a moment of disrespect, I asked, "Would you speak to your Sunday School teacher that way?"
"No ma'am."
"Would you speak to Pastor David that way?"
"No ma'am."
"Would you speak to [the next door neighbor, your swim coach, your Aunt Chris, a complete stranger...] that way?"
"No ma'am."
"Then you may not speak to me that way."

I've made her repeat what she says to me over and over this morning, until she can say what she wants to say with the proper tone and inflection.
I will not accept this:
"No MA'AM!!!!" (sass)
"No ma'am." (sullen)
"NO, THAT'S NOT WHAT I WAS EVEN DOING! I WAS JUST TRYING TO ...." (you get the point, I'm sure.)

Oh, I can hardly WAIT until she is an actual teen ager.