Translation:Miss Li is our manager.
In fact Ms is a much better translation of 小姐 than Miss. Even after marriage Chinese women will use 小姐, so like Ms it applies to married/unmarried females, just as MR does with males.
If 李小姐 married 王先生 she would still be known by everyone as 李小姐.
王太太 would be used only by strangers.