Ok, this is definitely something that sounds like a stupid question, since we all know the general rule about high heels, and wood flooring. However, I can't help but wonder if there is any way to finish douglas fir flooring to make it able to withstand the pressure of high heels.

Ooops, for some reason I deleted Pete's response by mistake.

That's what I get for not waking up first.

That's ok. Maybe he'll get around to typing it up again.

Fir is a soft wood, about one half as hard as red oak. There is no way to make it harder.
High heels can be worn on a fir floor when the person tip-toes so not as much pressure is directed to the heel.
I know of a ballroom dance teacher who checks the tips of heels before class to see if the rubber tip is missing. He has seen denting and gouging of his maple floors from missing taps. Maple is even harder than oak.
The missing tip exposes a nail and the tip is small diameter.
It all comes down to pressure per square inch.
Best to not trust high heels on fir flooring.
Plain sawn fir is even more fragile than vertical grain flooring.