3 eggs, for 3 daughters, so why the other women?

Why the other women? Because they wanted to use commoners as sacrifices instead of their actual bloodline.

There was an episode of Star Trek where an alien said they couldn't really tell the difference between humans because we all look alike. Just because we know the difference doesn't mean a dragon (or even an alien) would. Maybe we all do look alike to it. A hive of bees all look alike to me, but I bet they would wonder why we can't tell them apart.

And plus, the dragon is going off scent, and those girls aren't around long enough for the dragon to do a visual study in those dark caves. I doubt any of them stood around and looked that dragon in the eye. She probably roasted most of them while they were on the run with their backs turned anyway.

I was wondering about it too.

The only reason i could come up with is that, Netflix formula director thought to make it this way to add more complexity to the script for making a map in the caves for the final act.

It's 3 daughters for each generation

There is a scene in the film where Elodie tries to escape by climbing up a cave covered in crystals, with the dragon opening its mouth below waiting for her to fall. This tells us that some damsel may be eaten. So, there could be many more victims than remains.

Imagine that some of them are smart enough to guess the story behind these dragon eggs and try to tell the dragon that their are not the daughter. But the dragon can smell the bloodline and know that people will say anything to save their lives. The only reason that Elodie is more convincing is because she was about to kill the dragon at the time, so there's no need to lie anymore.

Now, you wonder how a white king or queen can have daughters of their own but different ethnicity. I'd rather leave your curiosity out there until you learn that in biology class. "There is no such thing as a dumb question." - Carl Sagan