Who is in our house?

Friday evening Cynthia and I decided to go out with another couple, the Lannen's, to a Greek restaurant called the Fat Olive.  Our friends have 3 kids and offered to have their ayi (domestic helper), Mei,  come to our house and watch both families' children while we went out.  Mason was going out with friends so he was not available to help.  Our friends' ayi has a cousin who has moved from the country to the city to try and get a job as an ayi and has been training with Mei at the Lannen's house.  The plan was to have Mei come to our house (she lives near us) and the Lannen's would bring their kids over and then we would head to the restaurant. About 6:30 our doorbell rang and I answered the door to greet Mei (neither Cynthia nor I had ever met Mei).  I welcomed her in and tried to strike up a brief conversation in Chinese.  I asked if she was Mei to which she replied "Bu shi, wo jiao ming zi Xun Ye."  (My name is Xun Ye)  So then I thought, "Okay, Mei must have sent her cousin to our house and the both of them would watch the kids"  This made sense to me as 5 kids can be overwhelming to one person and this was probably just another opportunity for Mei to train her cousin.  Cynthia came in the room and quickly said "Hello" and promptly directed me to get her started on cutting up some brownies and washing the pan they were baked in.  I did my best to communicate this to which she quickly responded.  Cynthia continued getting ready and while doing socalled the Lannen's and asked "Why did Mei send her cousin? I thought Mei was coming."  Jill replied, "Mei is coming over - she should be there now".  "No, this is definitely not Mei." Cynthia replied followed by "Jill, who is in my house?" In the meantime, I was talking to our "mystery ayi" in my broken Chinese to realize that she had two children, was originally from Shanghai both of which did not fit the description of Mei or her cousin.  Mason was getting ready to head out and I called on him for assistance to talk to her and find out who she was and why she was here.  As Mason questioned her it became apparent to all of us that she was in the right number apartment - 301 - but in the wrong building!  She politely told Mason that she was going to go out for a "walk" and she left.  Not 2 minutes later did the doorbell ring again and Mei showed up (with no cousin) followed immediately by the Lannen's who happened to see the "mystery ayi" driving away on her scooter.  We retold the story, all had a nervous laugh and proceeded to have a great evening.