Because they live on the other side of the city.
句意:为什么温迪不能和她的同事交朋友?
根据原文第一段第二三行:
You can't really make friends with workmates, because they live on the other side of the city.
(你不能真正地和同事交朋友,因为他们住在城市的另一边。)
可知,温蒂不能和她的同事交朋友的原因是同事们住在城市的另一边。
故答案为Because they live on the other side of the city.