In this case it is necessary in order to show that we are speaking to a female. It is a correct sentence without the nikud, but we would need context to show whether a male or female is being spoken to.
In addition to the previous answer: nikud is almost always omitted in day to day Hebrew anyway, but the final khaf is a very rare example of it often being put in (in handwriting that is, on computer it's more difficult). This is not mandatory though.
There are sometimes, it depends on the editor of the book. I personally like it when nikkud is added for foreign names, for example.