Ilyas took a chair and sat next to the bed when Heaven told him to stay. If Zarin came back, she didn't have the energy to deal with him, so having Ilyas there made her feel relaxed.
For a moment she had thought it was Zamiel who came to her. She had panicked. She didn't want him to see the situation she was in with the person she called a friend. For the first time she was ashamed to call Zarin her friend, so she was glad that it was Ilyas who came to her.
They communicated through the necklace and the bracelet which let him know where she was when they needed to meet, so he must have used it.
"Thank you for staying." She told him.