(The whole time I was wondering: "who is this lady and what has she done with my mother!" )
That's simple. Her previous technique of being a hard ass, has failed, and this is a last ditch effort to manipulate and control you.
By behaving this way, she now has you questioning the decision that you've made. Don't let her current passive agressive behavior dictate your life.
If you were to change your mind and go back, it will soon be the same old thing again.
You made the right choice by beginning an adult life.