I think he just does not like her play style. She likes high balls and Ze does not likes that.
The problem is, there`s no doubt Sheilla was one of the best OPP in the World. But with that, Ze Roberto never really gave anyone else a true chance in the NT. Of course no one would take Sheilla`s place, but still Sheila started every single competition played, that includes even not important Grand Prix games and friendly games as well. He could have given others some chances as well.
In 2015 Sheilla took the year off and Joyce played the Grand Prix, and Joyce herself said she tried her best but her game does not fit with the NT.
Sheilla and Dani Lins played and started all 2016 Grand Prix games, he could let Tandara and Roberta play a little at least to show what they can do, but Ze Roberto did not think that way.