I just think Singapore would be a better fit for her. It's good to hear that some folks have put together an answer key. I'll look into it. When I follow along with the TM it takes almost an hour to do the lesson. I have tried to let my daughter do the worksheets herself, but she still needs me to teach her and give her lots of examples.
Horizons does use the spiral approach.
Singapore does not. I have only used Singaprore with K dd this year. I am hoping to move my 2nd grade dd into Singapore next year. Horizons is good too, just too academic for us. DD says its just too hard for her.