You can't really argue the logic without knowing the rationale. As I said in my original response to you:
"Perhaps the design of the piece fit the OP’s décor/desires but the color did not."
Your reasons for not painting teak are all perfectly valid. For all we know (which is not much) nancy's reasons *for* painting it may also be perfectly valid. You appear to be of the opinion that there is never a reason to paint teak. I don't have that strong of an overall, unbending opinion. I'm *not* saying that nancy did the right thing by painting it, I'm just saying that until I know *why* she painted it, I can't say that she shouldn't have.
A personal example:
I built this bench for my adult daughter. It's 5 ft long, built from rough sawn poplar that I milled to size. It's really quite pretty in it's natural form.
People have quietly said to me "Isn't it a shame that she painted that beautiful bench *pink*? You must be so disappointed." I always politely respond "First, it's her bench. What kind of gift would be if I dictated how it should be finished or didn't accept her choice? Second, you have to admit that it fits the décor perfectly."
Apples and oranges - unless nancy comes back and tells that she painted the piece to protect it from the elements. Your example of sanding is a great example of unnecessary
- and probably detrimental - work, just like painting teak for protection would be. However, if you can accept that there might be other reasons why she painted it, you will see that your example may not fit the situation.