I'm an adult skate and sometime I help other adults who're also trying to get more comfortable turning the "opposite" way. Most of the time I find the problem is with their shoulders - they tense up and lock their shoulders and upper body, preventing them from smoothly turning the direction less comfortable to them. Focusing on relaxing the shoulders and opening them in the direction they want to turn is usually key.
Another thing that helps is trying the steps and turns with little or no speed, and progressively increasing your speed when turning.
And of course, practice practice practice
This a thousand times. Back inside threes on my right foot are the bain of my life, and it's so easy to see why, on the left foot, my upper body shoulders and head all move in the correct direciton for the turn, and on the right foot they are barely even sqaure. I'm tense as anything in anticipation of the turn and then when my coach tells me to look to the right, instead I bring my right shoulder back to my chin instead of actually looking to the right I know, this, my coach knows this, but can I tell my body what to do....apparently not.