Elle was not lying when she told Sandy that she was on the way now, going to XXX Crime Investigation Headquarters. As Erick gave Elle a ride this morning, they talked about the collaboration requested by her in which the Unit Head denied.
It turned out Erick was the only one who made that decision. The Unit Head was not consulted at all. He said that because he just wanted to avoid working with Elle after he learned that she became James's fiancee.
Since Erick and Elle already reconciled with each other, she would continue covering Catseye's case for the purpose of catching Catseye and unfolding his identity.
After hearing Sandy's reaction over the phone, Elle could tell that she was upset about this. She didn't want to do this but since she was part of Aliyah's team, she had no choice but to comply.