My wife doesn't like any of the terms and would rather not be called by her size.

I do it anyway.

I've never heard of the word you're referring to being a slur, and only won't post it out of respect for the possibility that someone might take it that way. "Treat others how they would like to be treated" and all that.

Then it was "little person," but that was always kinda demeaning.

Dwarfism is the medical term, but then again "the R word" is a scientific term to mean "to slow the flow of" and we're definitely not allowed to say that. Remember when the Black Eyed Peas nearly got canceled for the song that is now known as Let's Get it Started? Never mind that the original song was not very good, in addition to being in poor taste. Anyway, as it turns out, "the scientific term" isn't always the most friendly term to use for marginalised groups.

The most modern way of addressing any disability or difference is to start with the person, so, that is to say, "person with dwarfism." But, by the same token, "person who is little" just seems demeaning. So, we loop back to my first statement. From which, inevitably, is followed by my second — but, that's my wife. Someone else? I'd just call them by their name.