Always Mad

I knew my daughter had problems talking to my husband, her stepdad, but tonight she totally had a melt down, saying every time she needs anything from him he always gets mad, reminding her of when things were really awful between us. She said that it causes her horrible stress and is interfering with her ability to take care of business she needs his help with.
Right now she needs him to pay a bill online for her school and is afraid he will get mad at her. I feel like the worst mother in the world for not seeing how bad this situation had gotten, and worse, for bringing him into her life.
I really hope their relationship will improve, if it doesn't I will feel terrible for the rest of my days.