It's Iman's (6 year old sister) turn.!

You know, most of the time, my maid will get disturbed by the ghost . Only this time, the ghost
'IS HER'! . This scene happened in the living room . There was only my maid and my youngest sister, Iman . At that time, Iman was watching the television, when my maid tried to pull a ghost prank on Iman . She knocked the window behind Iman, and when Iman turned back, she saw the maid . And when the maid came in and rearranged the shoes in the shoerack, there was someone knocking at the window. Iman said "bibik!" and she totally saw the maid, except she is wearing other kind of shirt . Right after Iman said 'bibik!', my maid who was INSIDE AT THE SHOERACK answered 'ya iman?!" Question is, who knocked the window right after my maid came in. And why did "IT" looked alike like the maid?