She had fish way back when when she was having dairy but hasn't had it since...just no idea how to make it for her.
Murray used to love tinned sardines and tuna (not now though!) - either alone, or mixed with pureed veggies. We now buy frozen fish which tells you on the back how to cook it - usually just shove it in the oven.
Remember even if you wouldn't eat it, kids probably will!! The more you adapt recipes the easier it is and the more confident you get. I used to be a recipe follower.