Rachel was left alone by the siblings inside Ezekiel's bedroom together with the unconscious Phoebe in order for her to change the clothes in which Phoebe was wearing. That was the main reason for why Ezekiel involved her in this complicated situation but aside from that, there were other considered reasons on why he chooses Rachel out of the hundreds of maids workers within the mansion.
Firstly he trusted her. Secondly, he could see no one in the entirety of the mansion which can take good care of Phoebe without any complains or troubles and thirdly, she was his nanny when he was a child. In all, her qualities were the reason.
Before he even called Rachel here, Ezekiel filled one of the wardrobes in his room, which was empty at first, with a different styles and sets of expensive sleeping dresses. Those were for her to use during her period of unconsciousness. He was pathetic.
