I don't know... She's not in Sakura Cafe closing events list as well. As for hiring other actress, I assume that making seiyuus play their roles is the most important part of this project. That's why Sumire got her retirement OVA when her seiyuu decided to leave the project. And Orihime, being a popular character, was not a Top Star (Takarazuka reference again), so she just left the stage quietly. Of course, it's just my theory.