Children are very aware of things as it relates to parents.
I believe that as you continue to better yourself and be the best dad possible that your D will know the truth regardless of your STBX.
My d17 saw throughly WAW nasty complaining of me for the past several years before the BD. She has chosen to stay with me because she believes what she see's not what she hears.
The best way to be sure d does not believe what STBX says is for her to see your actions. Kids are very aware. More than we can ever know.
Me 46 Former W 46 D19 D7 BD Feb 2016 WAW moves out 4/16/16 D final 6/1/2017
It's time for me to start changin' the way I look at the world......and at myself. ~James Howlett aka Wolverine