Why did he say to call her?
Radak: She already departed from in front of him.
Before (verse 12), she stood in front of him. Why did she now stand in the doorway?
Pirkei d'R. Eliezer 32: She was unable to look at his face, lest she die. Kli Yakar - before she looked down. Danger is more stringent than Isur. Now she did not even stand in front of him, lest she look at his face.
Kli Yakar citing Mahari: Before, she stood in front of him to get grace in his eyes for what she did for him. Now he called her, so she herself will hear Devar Hashem. She stood in the doorway due to modesty.
Kli Yakar citing Mahari, Malbim: She saw that he did not speak to her in the second person (he told Gechazi to speak to her - verse 13). I.e. he does not speak with women. Therefore, she did not enter his room.
