Dixie Chicked

I made my bed and I sleep like a baby
With no regrets and I don’t mind sayin’
It’s a sad sad story when a mother will teach her
Daughter that she ought to hate a perfect stranger
And how in the world can the words that I said
Send somebody so over the edge
That they’d write me a letter
Sayin’ that I better shut up and sing
Or my life will be over

What the heck are they singing about?