Stella decided to commute home every day since Zafir said he would be in Nigellus for a while.
She wanted to be able to spend some time with him before he heads to Alvarez since she might not see him ever again.
It would simply be sad since he had been her confidante for so long. There were things she couldn't tell him but he was the one who was always with her. She tells him most of her rants and problems and he listens to her without any complaints.
Zafir wasn't excessive like Hendrick so she could be honest with her thoughts and just say as she pleases most of the time.
She had gotten close to Sarah and her other maids but their difference in rank had kept the distance between them. Her maids were scared to be too close because Hendrick might see it as them being disrespectful and have them punished.