clientsfromhell:

Client: My daughter has taken a college English course and she says that every instance of “that” needs to be “which” and the opposite in all instances in the book.

Me: Actually, they’re all correct as is, honoring the standard “that” for restrictive and “which” for non-restrictive.  For example, it would properly be, “The dog that my aunt had, which was a mixed breed, was named Whoknows.” If one were to follow your directive above, it would incorrectly read, “The dog which my aunt had, that was a mixed breed, was named Whoknows.”  

Client: She took a college English course.

Me: With all due respect, I majored in it, plus I have 30 years of editing experience. 

Client: I’m sure the rule has changed since you were in college.  Maybe you should take a refresher to catch up on current rules.

I billed for hours in and gently ended my association with that (not which) project.